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Fish Biology Overview
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Fish Biology Overview

Created by
@EffectiveOnyx3989

Questions and Answers

Which classes of vertebrates are generally considered fish?

  • Mammals and birds
  • Amniotes and jawless fish
  • Amphibians and reptiles
  • Sharks and rays, and bonyfish (correct)

    • What percentage of known fish species are found in marine environments?

  • 58% (correct)
  • 25%
  • 90%
  • 75%

    • What is the smallest unit in the hierarchical classification of organisms?

  • Species (correct)
  • Class
  • Genus
  • Family

    • Which environment hosts the highest number of fish species according to the document?

    <p>Warm and temperate waters of continental shelves</p> Signup and view all the answers

    In binominal nomenclature, how is the genus name presented?

    <p>In italics and capitalized</p> Signup and view all the answers

    How many species are estimated to inhabit the cold polar waters?

    <p>Around 1,100 species</p> Signup and view all the answers

    Which of the following is true regarding fish species distribution?

    <p>There are about 1,000 species of mid-water fish in the mesopelagic zone</p> Signup and view all the answers

    What is the proper classification hierarchy from species to kingdom?

    <p>Species: Genus: Family: Order: Class: Phylum: Kingdom</p> Signup and view all the answers

    What is the primary reason scientific names should be used in publications?

    <p>They eliminate confusion caused by local names.</p> Signup and view all the answers

    Which group of fish is classified as having a high urea content in muscle?

    <p>Chondrichthyes</p> Signup and view all the answers

    What distinguishes demersal fish from pelagic fish?

    <p>Their feeding habits.</p> Signup and view all the answers

    How do fish muscle cells differ from those of terrestrial mammals?

    <p>They lack a tendinous system.</p> Signup and view all the answers

    What is the role of the myocommata in fish anatomy?

    <p>To anchor muscle cells to the skin and skeleton.</p> Signup and view all the answers

    Which factor causes dark muscle to be more prevalent in pelagic fish?

    <p>Continuous swimming and activity levels.</p> Signup and view all the answers

    What type of muscle tissue is predominant in most fish?

    <p>Striated muscle.</p> Signup and view all the answers

    Why is the presence of lipids significant in the muscle tissue of fish?

    <p>They can cause rancidity in fish products.</p> Signup and view all the answers

    Which pigment is responsible for the reddish color in salmon and sea trout?

    <p>Astaxanthin.</p> Signup and view all the answers

    Which classification group contains jawless fish?

    <p>Cyclostomes.</p> Signup and view all the answers

    What anatomical feature runs the full length between two myocommata in fish?

    <p>Muscle cells.</p> Signup and view all the answers

    What is the distinctive characteristic of bony fish muscles compared to cartilaginous fish muscles?

    <p>Structure of the muscle tissue.</p> Signup and view all the answers

    Which statement about false ribs in fish is true?

    <p>They extend into the muscle tissue and can complicate filleting.</p> Signup and view all the answers

    Where do the longest muscle cells in cod typically occur?

    <p>Around the twelfth myotome from the head.</p> Signup and view all the answers

    What is the recommended bleeding period for fish before they are gutted?

    <p>15-20 minutes</p> Signup and view all the answers

    What complication arises from the two-step procedure of bleeding followed by gutting?

    <p>Time-consuming for fishermen</p> Signup and view all the answers

    Which factor is most critical for achieving the best bleeding results in fish?

    <p>Time spent onboard prior to bleeding</p> Signup and view all the answers

    What did Huss and Asenjo find about the cutting method for optimal bleeding?

    <p>A deep throat cut including the dorsal aorta is optimal</p> Signup and view all the answers

    Which organs in fish are recognized as major foodstuffs?

    <p>Roe and liver</p> Signup and view all the answers

    What changes occur in cod muscle prior to spawning?

    <p>Decrease in protein content</p> Signup and view all the answers

    At what stage do most fish become sexually mature?

    <p>When they reach a size characteristic of the species</p> Signup and view all the answers

    Which fish species is known to only migrate once before degenerating and dying?

    <p>Atlantic salmon</p> Signup and view all the answers

    What happens to the lipid content during migration in Pacific salmon?

    <p>Decreases by 92%</p> Signup and view all the answers

    How does the growth process affect muscle cells in fish?

    <p>The size of each muscle cell increases</p> Signup and view all the answers

    Which of the following statements relates to the weight of a fish prior to spawning?

    <p>The fish's water content can reach up to 87% of body weight</p> Signup and view all the answers

    What is a secondary effect of rough handling of fish during capture?

    <p>Discoloration of the fillet</p> Signup and view all the answers

    What occurs to fish reserves during gonadal development?

    <p>Depletion of protein and lipid reserves occurs</p> Signup and view all the answers

    What is the lifespan of North Sea cod in relation to spawning?

    <p>They can live for about 8 years before dying from spawning</p> Signup and view all the answers

    What is one key attribute of the fish heart's design?

    Signup and view all the answers

    What is the primary reason for including astaxanthin in fish feed during aquaculture?

    <p>To improve the red color of the flesh</p> Signup and view all the answers

    What is the role of Ca++ in muscle contraction according to physiological processes described?

    <p>Ca++ activates ATP-ase to release energy</p> Signup and view all the answers

    Why do salmonids living in waters with little carotenoid exhibit less red muscle color?

    <p>They depend on external sources of carotenoids for muscle color</p> Signup and view all the answers

    What is a major difference between light muscle and dark muscle in fish?

    <p>Dark muscle supports prolonged, low-intensity activity</p> Signup and view all the answers

    What happens to muscle fibers when ATP levels reach a minimum post-mortem?

    <p>Muscle fibers contract and become interconnected irreversibly</p> Signup and view all the answers

    How does the cardiovascular system of fish differ from that of mammals?

    <p>The fish heart consists of two chambers</p> Signup and view all the answers

    What occurs during blood circulation in a fish after blood passes through the gills?

    <p>Arterial blood collects in the dorsal aorta</p> Signup and view all the answers

    How does the blood volume distribution in fish relate to muscle tissue?

    <p>Only 20% of blood volume is in the muscular tissues</p> Signup and view all the answers

    What physiological function primarily prevents counterflow of blood in fish veins?

    <p>Presence of paired valves in veins</p> Signup and view all the answers

    What is the consequence of inadequate carotenoid ingestion in fish from low-carotenoid waters?

    <p>Loss of distinctive flesh coloration</p> Signup and view all the answers

    Why is muscle contraction important for blood circulation in fish?

    <p>It aids in returning blood to the heart</p> Signup and view all the answers

    What happens to lactic acid produced in light muscle during anaerobic metabolism?

    <p>It is transported to the liver for metabolization</p> Signup and view all the answers

    What physiological change occurs in fish muscle at spawning time?

    <p>Muscle color fades significantly</p> Signup and view all the answers

    What is the effect of post-mortem conditions on the ATP levels in fish muscle?

    <p>ATP levels decline until a minimum is reached</p> Signup and view all the answers

    What occurs to fish muscle immediately after death?

    <p>The muscle completely relaxes.</p> Signup and view all the answers

    How does high temperature affect rigor mortis in cod?

    <p>It accelerates the onset and increases rigor strength.</p> Signup and view all the answers

    Which factor does NOT affect the rate of onset and resolution of rigor mortis in fish?

    <p>Length of the fish</p> Signup and view all the answers

    What is the typical duration of rigor mortis after it begins?

    <p>A day or more.</p> Signup and view all the answers

    What phenomenon may occur due to strong rigor tensions in fish?

    <p>Gaping of the fillet.</p> Signup and view all the answers

    What effect does cooler storage temperature have on the onset of rigor mortis in some tropical fish species?

    <p>It accelerates the onset.</p> Signup and view all the answers

    Which of the following statements is true regarding sensory changes in fish during storage?

    <p>Appearance changes are the most noticeable immediately after death.</p> Signup and view all the answers

    Why is it generally accepted that the onset and duration of rigor mortis occur more rapidly at higher temperatures?

    <p>Higher temperatures speed up biochemical changes.</p> Signup and view all the answers

    What is the primary factor that differentiates firm and elastic flesh from soft flesh in fish?

    <p>Elasticity and firmness</p> Signup and view all the answers

    What happens to the pH of cod muscle post-mortem as anaerobic glycolysis occurs?

    <p>Decreases from 6.8 to 6.1-6.5</p> Signup and view all the answers

    What visual characteristics indicate a fresh fish's eyes?

    <p>Convex and transparent</p> Signup and view all the answers

    How do enzymatic changes in fish affect freshness compared to bacterial spoilage?

    <p>Enzymatic changes always precede bacterial spoilage in all species.</p> Signup and view all the answers

    What is indicated by a yellowish color in the gills of fish?

    <p>Some discolouration</p> Signup and view all the answers

    In what condition is the flesh of fish described as velvety or waxy?

    <p>Deteriorating</p> Signup and view all the answers

    What is the consequence of oxygen deprivation in fish muscle immediately post-mortem?

    <p>Anaerobic glycolysis begins</p> Signup and view all the answers

    What does a score lower than 4 signify on the sensory evaluation scale for fish?

    <p>The fish is spoiled</p> Signup and view all the answers

    What type of respiration is primarily responsible for ATP production after a fish dies?

    <p>Anaerobic respiration</p> Signup and view all the answers

    What indicates that the kidneys and organ residues in fish have started to spoil?

    <p>Brownish color</p> Signup and view all the answers

    Which sensory characteristic should be present in the gills of fresh fish?

    <p>No mucus</p> Signup and view all the answers

    Which of the following best describes the flesh condition when it sticks to the peritoneum?

    <p>Deteriorating</p> Signup and view all the answers

    What end-products are generated from anaerobic metabolism during fish post-mortem?

    <p>Lactic and pyruvic acids</p> Signup and view all the answers

    Which factor strongly influences the degradation rate of chilled fish compared to ambient conditions?

    <p>Temperature</p> Signup and view all the answers

    What is the effect of stunning and killing fish by hypothermia on the onset of rigor mortis?

    <p>It results in the fastest onset of rigor.</p> Signup and view all the answers

    What occurs to muscle fibers after ATP levels fall post-mortem?

    <p>Muscle fibers lose elasticity and stiffness occurs.</p> Signup and view all the answers

    How does the texture of fish change when cooked post-rigor compared to pre-rigor?

    <p>It is tough but not dry.</p> Signup and view all the answers

    What is the expected change in length of dark muscle when cooked pre-rigor?

    <p>It shrinks by up to 52%.</p> Signup and view all the answers

    Which phase characterizes the very fresh fish with a sweet taste after catching?

    <p>Phase 1</p> Signup and view all the answers

    What impact does rough handling of fish during capture have on fileting yield?

    <p>It causes gaping in the muscle tissue.</p> Signup and view all the answers

    How does the state of glycogen reserves affect the onset of rigor mortis in fish?

    <p>Depleted glycogen causes an immediate onset.</p> Signup and view all the answers

    Which of the following factors primarily affects the sensory evaluation of raw fish?

    <p>Appearance, texture, and odour</p> Signup and view all the answers

    What happens to fish fillets if they are frozen pre-rigor and then thawed at low temperatures?

    <p>The rigor mortis process can proceed properly.</p> Signup and view all the answers

    What occurs during Phase 3 of fish spoilage?

    <p>Off-flavors begin to develop.</p> Signup and view all the answers

    Which species demonstrates the shortest time from death to onset of rigor when stressed?

    <p>Cod</p> Signup and view all the answers

    What is a characteristic change in fish that is very fresh when compared to stored fish?

    <p>It has a sweet, seaweedy, and delicate taste.</p> Signup and view all the answers

    What does the term 'post-rigor' refer to in the quality of fish?

    <p>The texture is firm, succulent, and elastic.</p> Signup and view all the answers

    When evaluating cooked fish, which phase indicates the first signs of spoilage?

    <p>Phase 3</p> Signup and view all the answers

    What is the typical pH range observed for large mackerel during rigor mortis?

    <p>5.8-6.0</p> Signup and view all the answers

    How does stored glycogen in fish generally compare to that in mammals?

    <p>Fish muscles have lower glycogen levels</p> Signup and view all the answers

    What effect does pre-capture stress have on the pH levels of fish muscle?

    <p>It lowers the pH level</p> Signup and view all the answers

    What is indicated by a high 'K' value in the context of fish freshness?

    <p>Low freshness level</p> Signup and view all the answers

    What is the role of ATP in muscle contraction?

    <p>It acts as a muscle plasticizer and energy source</p> Signup and view all the answers

    Why are fish in rigor mortis unsuitable for processing?

    <p>Their muscle is too stiff to manipulate</p> Signup and view all the answers

    What does the breakdown of ATP in post-mortem fish muscle indicate?

    <p>Degradation of muscle texture</p> Signup and view all the answers

    Which nucleotide is associated with the desirable fresh fish flavor?

    <p>IMP</p> Signup and view all the answers

    What happens to the water-holding capacity of fish muscle as post-mortem pH drops?

    <p>It decreases due to protein denaturation</p> Signup and view all the answers

    According to the autolytic changes after death, which compound is one of the first to degrade?

    <p>ATP</p> Signup and view all the answers

    What does the term 'rigor mortis' refer to in fish muscle?

    <p>Stiffening of muscle after death</p> Signup and view all the answers

    What is a consequence of muscle tissue being in rigor mortis during processing?

    <p>Difficulties in filleting</p> Signup and view all the answers

    Which factor does NOT affect the levels of stored glycogen in fish before death?

    <p>Water temperature</p> Signup and view all the answers

    What occurs during the resolution of rigor in fish muscle?

    <p>Softening of muscle tissue</p> Signup and view all the answers

    What is the role of the TMAO-ase enzyme in fish?

    <p>It contributes to the toughening of muscle tissue.</p> Signup and view all the answers

    What can minimize the production of formaldehyde during frozen storage of fish?

    <p>Freezing fish at temperatures lower than -30°C.</p> Signup and view all the answers

    Which organ in gadoid fishes is primarily associated with the presence of TMAO demethylase?

    <p>Kidney</p> Signup and view all the answers

    What impact does rough handling of fish during capture have on their quality?

    <p>It accelerates autolytic changes and protein breakdown.</p> Signup and view all the answers

    The softening of tissue due to collagenases is primarily associated with which factor?

    <p>Autolytic changes during freezing.</p> Signup and view all the answers

    Which of the following statements about the production of formaldehyde in fish is accurate?

    <p>The amount of formaldehyde produced is equivalent to dimethylamine formed.</p> Signup and view all the answers

    What is one critical factor in preventing 'gaping' of fish fillets during storage?

    <p>Ensuring fish are frozen immediately after capture.</p> Signup and view all the answers

    In terms of muscle activity, how does dark muscle differ from white muscle in gadoid fish?

    <p>Dark muscle has a higher rate of enzymatic activity.</p> Signup and view all the answers

    What is a recommended practice to minimize the toughening of hake muscle during frozen storage?

    <p>Minimize exposure to temperature fluctuations.</p> Signup and view all the answers

    Which enzyme class is responsible for the softening of connective tissues in fish?

    <p>Collagenases</p> Signup and view all the answers

    What is indicated by the equal rates of formation and breakdown of IMP in sterile and non-sterile cod tissue?

    <p>It results from the action of autolytic enzymes.</p> Signup and view all the answers

    What effect does physical handling have on autolytic changes in chilled fish?

    <p>It accelerates the autolytic changes.</p> Signup and view all the answers

    What role does bacterial nucleoside phosphorylase play in refrigerated cod?

    <p>It accelerates the conversion of Iino to Hex.</p> Signup and view all the answers

    Which enzyme is primarily responsible for the degradation of ATP through to inosine?

    <p>Bacterial nucleoside phosphorylase</p> Signup and view all the answers

    What is a consequence of the autolysis of fish muscle tissue?

    <p>Acceleration of spoilage bacteria growth.</p> Signup and view all the answers

    Which factors primarily influence belly-bursting in herring?

    <p>Physical handling practices.</p> Signup and view all the answers

    What characteristic is associated with the cathepsins found in fish tissues?

    <p>They are inactive in living tissue.</p> Signup and view all the answers

    What is the effect of autolytic proteolysis on pelagic fish during the summer months?

    <p>It can lead to belly-bursting.</p> Signup and view all the answers

    Which of the following is NOT a factor in the rates of nucleotide degradation among different fish species?

    <p>Size of the fish.</p> Signup and view all the answers

    Which proteolytic enzymes have been investigated for their role in fish tissue breakdown?

    <p>Carboxypeptidases and chymotrypsin</p> Signup and view all the answers

    Which process can inhibit proteolysis in fish muscle tissue?

    <p>Addition of potato extracts</p> Signup and view all the answers

    What pH range do cathepsin D enzymes predominantly exhibit activity?

    <p>3-8</p> Signup and view all the answers

    What was a significant finding related to nucleotide breakdown rates in bulk-stored herring for fishmeal?

    <p>Autolysis strongly influences commercial viability.</p> Signup and view all the answers

    Why is it important to store iced fish in boxes that are not deeper than 30 cm?

    <p>To minimize pressure that can accelerate autolysis.</p> Signup and view all the answers

    Which statement is true regarding the activity of cathepsins in fish tissues?

    <p>They are activated upon physical damage.</p> Signup and view all the answers

    What is the primary reason cathepsin L is implicated in the softening of salmon muscle during spawning?

    <p>It degrades connective tissues effectively.</p> Signup and view all the answers

    Why is it unlikely that Reddi's enzyme was active in salted fish products?

    <p>Salt strongly inhibited the enzyme activity.</p> Signup and view all the answers

    How does freezing and thawing affect autolytic enzyme activity in fish muscles?

    <p>It enhances the activity of membrane-bound enzymes.</p> Signup and view all the answers

    Which enzymes are primarily responsible for the post mortem autolysis of meat?

    <p>Calpains.</p> Signup and view all the answers

    What effect does cathepsin L activity have on muscle texture during the fermentation process of fish products?

    <p>It induces major textural changes.</p> Signup and view all the answers

    Which type of collagen has been linked to the gaping or breakdown of myotomes during long-term storage of fish?

    <p>Type V collagen.</p> Signup and view all the answers

    How does calpain activity in fish compare to that in mammalian muscle?

    <p>Calpain activity is higher in fish and more specific.</p> Signup and view all the answers

    What is the significance of calcium in the activity of calpains?

    <p>Calcium is a cofactor required for calpain activation.</p> Signup and view all the answers

    Which statement accurately describes the role of collagenases in fish?

    <p>They help solubilize connective tissue during storage.</p> Signup and view all the answers

    What happens to tropical fish species in terms of calpain autolysis compared to those adapted to colder environments?

    <p>They are less susceptible due to higher heat stabilities.</p> Signup and view all the answers

    Which major consequence does high calpain activity have on the quality of fish muscle?

    <p>Leads to undesirable softness.</p> Signup and view all the answers

    What is a significant factor influencing calpain activity in fish species?

    <p>Muscle temperature during storage.</p> Signup and view all the answers

    What is one of the attributes of proteolytic enzymes in parasitized Pacific hake muscle?

    <p>Their origin (parasite or host) remains unclear.</p> Signup and view all the answers

    What notable difference exists between myosins in fish and mammals concerning calpain action?

    <p>Fish calpain digests myosin more effectively.</p> Signup and view all the answers

    What is the first sensory change in fish during storage?

    <p>Change in appearance</p> Signup and view all the answers

    What condition does fish undergo immediately after death?

    <p>Rigor mortis</p> Signup and view all the answers

    How does high temperature affect the onset of rigor mortis in cod?

    <p>It causes rapid onset with strong rigor</p> Signup and view all the answers

    Which factor does NOT affect the rate of onset and resolution of rigor mortis?

    <p>Color of the fish</p> Signup and view all the answers

    What physiological change occurs in the fish muscle after rigor mortis resolves?

    <p>Becomes limp but less elastic</p> Signup and view all the answers

    What is the relationship between temperature and the onset of rigor mortis in certain tropical fish?

    <p>Rigor onset is delayed at higher temperatures</p> Signup and view all the answers

    What can be a consequence of strong rigor tensions in fish?

    <p>Weakening of connective tissue</p> Signup and view all the answers

    What does the onset of rigor mortis depend on in carp, according to research?

    <p>Sea temperature versus storage temperature</p> Signup and view all the answers

    What effect does stress have on the onset of rigor mortis in fish?

    <p>It triggers an immediate onset of rigor mortis.</p> Signup and view all the answers

    How does the method of stunning affect rigor mortis in fish?

    <p>Stunning by hypothermia leads to the fastest onset of rigor.</p> Signup and view all the answers

    What happens to muscle contraction when fish are filleted pre-rigor?

    <p>The muscle may contract freely but will immediately become stiff.</p> Signup and view all the answers

    Which of the following best describes the texture of fish cooked post-rigor?

    <p>Firm, succulent, and elastic.</p> Signup and view all the answers

    What does the onset time of rigor mortis depend on?

    <p>Type of storage method and the temperature.</p> Signup and view all the answers

    What phase indicates the fish has become spoiled and putrid?

    <p>Phase 4</p> Signup and view all the answers

    What is the effect of cooking fish in rigor compared to cooking pre-rigor?

    <p>Fish cooked in rigor is tough but not dry.</p> Signup and view all the answers

    During which phase does the fish begin to lose its characteristic odour and taste?

    <p>Phase 2</p> Signup and view all the answers

    What is the maximum shrinkage of dark muscle according to the content?

    <p>52%</p> Signup and view all the answers

    What happens during the cooking of fillets removed pre-rigor?

    <p>They may have a soft and pasty texture.</p> Signup and view all the answers

    What condition indicates a fish is in a ‘1’ state for flesh inspection based on its surface characteristics?

    <p>Soft and flaccid with a wrinkled surface</p> Signup and view all the answers

    Which of the following statements about the appearance of fish before and after storage is true?

    <p>Chilled fish spoil faster than iced fish despite appearance.</p> Signup and view all the answers

    In the context of fish freshness, which gill condition would indicate a decline in quality?

    <p>Discolored gills with opaque mucus</p> Signup and view all the answers

    Which assessment method should be conducted to determine the quality of chilled fish during storage?

    <p>Sensory assessment of cooked fish.</p> Signup and view all the answers

    Which aspect of the fish's visual inspection should be evaluated first for overall quality assessment?

    <p>Skin appearance</p> Signup and view all the answers

    Which of the following factors is NOT relevant when assessing the condition of the fish's flesh?

    <p>Quantity of scales</p> Signup and view all the answers

    What is the correct pH range of cod muscle during post mortem changes?

    <p>6.0 to 6.5</p> Signup and view all the answers

    What physiological change occurs in fish muscle tissue shortly after death?

    <p>Initiation of lactic acid accumulation</p> Signup and view all the answers

    Which of the following is a characteristic of autolytic changes in fish spoilage?

    <p>Independent of microbial processes</p> Signup and view all the answers

    How does internal energy production in fish muscles occur after death?

    <p>Mainly through anaerobic pathways</p> Signup and view all the answers

    Which of the following pathways is NOT involved in ATP production in post mortem fish muscle?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    What happens to the freshness indicators of fish when they fall below a sensory evaluation score of 4?

    <p>Reflects spoiled fish quality</p> Signup and view all the answers

    What characteristic is used to describe a ‘1’ state in the eye inspection of fish?

    <p>Concave in the center with a grey pupil</p> Signup and view all the answers

    What is the significance of the bright red color of the kidneys and other organs in fish?

    <p>Marker of absolute freshness</p> Signup and view all the answers

    What effect does rigorous post mortem handling have on fish tissue?

    <p>Leads to faster spoilage</p> Signup and view all the answers

    What is the primary enzyme responsible for autolysis in salmon muscle during spawning?

    <p>Cathepsin L</p> Signup and view all the answers

    How does sodium chloride (NaCl) affect enzyme activity in the context of fish muscle?

    <p>It strongly inhibits enzyme activity.</p> Signup and view all the answers

    Which statement best describes the relationship between cathepsin L activity and the texture of fish muscle?

    <p>Increased cathepsin L activity correlates with softer muscle texture.</p> Signup and view all the answers

    What role do calpains play in the texture changes of fish muscle?

    <p>They are responsible for post mortem autolysis of meat.</p> Signup and view all the answers

    Which factor is most likely to enhance autolytic activity in fish muscle during storage?

    <p>Freezing and thawing processes.</p> Signup and view all the answers

    What is the effect of high temperature on connective tissue in fish muscle?

    <p>It leads to gaping due to collagen degradation.</p> Signup and view all the answers

    What distinguishes fish calpains from mammalian calpains?

    <p>Fish calpains specifically digest myosin heavy chain.</p> Signup and view all the answers

    Which enzyme is implicated in the jelly-like softening of flounder muscle?

    <p>Cathepsin L</p> Signup and view all the answers

    What is a primary characteristic of the degradation process mediated by collagenases in fish muscle?

    <p>They cause breakdown of myotome structure.</p> Signup and view all the answers

    What are the primary conditions that activate calpains in fish?

    <p>The availability of cysteine and calcium.</p> Signup and view all the answers

    What is the effect of the presence of catheptic enzymes on fermented fish products?

    <p>They induce intentional autolytic changes.</p> Signup and view all the answers

    In terms of fish autolysis, how do myofibrillar proteins contribute to muscle texture?

    <p>They contribute to texture changes when digested by cathepsins.</p> Signup and view all the answers

    What role does the degradation of type V collagen play in the texture of fish muscle?

    <p>It is linked to the gaping phenomenon during storage.</p> Signup and view all the answers

    What is the primary enzyme responsible for the toughening of frozen gadoid fish?

    <p>TMAO-ase</p> Signup and view all the answers

    Which factor significantly accelerates the breakdown of fish flavor due to nucleotide degradation?

    <p>Rough handling or crushing</p> Signup and view all the answers

    How can toughening of frozen fish muscle be minimized during storage?

    <p>By ensuring kidneys are removed from the fish</p> Signup and view all the answers

    What change occurs in chilled prawns due to collagenase enzymes?

    <p>Softening of the tissue</p> Signup and view all the answers

    What is the byproduct of TMAO breakdown that poses a greater commercial significance?

    <p>Formaldehyde (FA)</p> Signup and view all the answers

    In which tissue is TMAO demethylase most commonly found?

    <p>Kidney</p> Signup and view all the answers

    What condition leads to high levels of formaldehyde production in frozen fish storage?

    <p>Frequent temperature fluctuations</p> Signup and view all the answers

    What is a consequence of the physical disruption of muscle cells in fish?

    <p>Accelerated autolysis</p> Signup and view all the answers

    How does dark muscle differ from white muscle in terms of TMAO demethylase activity?

    <p>It has a higher activity level</p> Signup and view all the answers

    Which of the following is NOT a factor involved in autolytic changes affecting fish edibility?

    <p>Bioaccumulation of toxins</p> Signup and view all the answers

    What is the main factor that influences the ultimate post mortem pH in fish?

    <p>Stored glycogen levels</p> Signup and view all the answers

    Which fish species is noted for having particularly low ultimate rigor pH levels?

    <p>Halibut</p> Signup and view all the answers

    What happens to the muscle protein's water-holding capacity as post mortem pH decreases?

    <p>It partially denatures, reducing capacity</p> Signup and view all the answers

    What happens to fish muscle as rigor mortis sets in?

    <p>Muscle becomes stiff and inextensible</p> Signup and view all the answers

    What is associated with the undesirable texture of fish muscle when the pH is low?

    <p>Higher protein denaturation</p> Signup and view all the answers

    How does bleeding fish affect lactic acid production post mortem?

    <p>It significantly reduces lactic acid production</p> Signup and view all the answers

    What is the consequence of a fish being stressed prior to capture in terms of its pH level?

    <p>Decrease of about 0.50 pH units</p> Signup and view all the answers

    Which nucleotide catabolite is primarily associated with the desirable flavor of fresh fish?

    <p>IMP</p> Signup and view all the answers

    What aspect of nucleotide degradation is considered unreliable for measuring fish freshness?

    <p>Variability in K value among species</p> Signup and view all the answers

    What is the primary role of ATP in muscle contractions?

    <p>Source of high energy for contractions</p> Signup and view all the answers

    Which change is NOT typically observed in fish muscle during autolysis?

    <p>Increase in ATP concentration</p> Signup and view all the answers

    What enzyme is primarily involved in muscle contraction and is affected during rigor mortis?

    <p>ATP-ase</p> Signup and view all the answers

    What can significantly affect the physical properties of fish muscle post mortem?

    <p>Pre-mortem stress levels</p> Signup and view all the answers

    Which enzyme is primarily responsible for the conversion of Iino to Hx in non-sterile cod samples?

    <p>Nucleoside phosphorylase</p> Signup and view all the answers

    What is the main consequence of physical handling on chilled fish?

    <p>Accelerates autolytic changes</p> Signup and view all the answers

    What effect do autolytic processes have on fish used for fishmeal production?

    <p>Enhance bacterial growth</p> Signup and view all the answers

    What is a notable consequence of belly-bursting in pelagic fish species?

    <p>Extensive softening of the tissue</p> Signup and view all the answers

    Which factor was found to influence belly-bursting in herring the most?

    <p>Freezing and thawing processes</p> Signup and view all the answers

    What is the primary role of cathepsins in fish tissue?

    <p>Degrade proteins at injury sites</p> Signup and view all the answers

    What impact does autolysis have on the nutritional value of fish?

    <p>Lowers the nutritional value</p> Signup and view all the answers

    What is one method that has been shown to inhibit proteolysis in fish?

    <p>Addition of potato extracts</p> Signup and view all the answers

    How does the activity of proteolytic enzymes change after physical abuse to fish?

    <p>Increases significantly</p> Signup and view all the answers

    How does the degradation of nucleotide catabolites differ between sterile and non-sterile cod fillets?

    <p>It is faster in non-sterile fillets</p> Signup and view all the answers

    What is a key reason to avoid stacking fish boxes too deeply?

    <p>To minimize autolysis</p> Signup and view all the answers

    What pH range is cathepsin D believed to be active in?

    <p>3-8</p> Signup and view all the answers

    What describes the compartmentalization of autolytic enzymes in fish tissues?

    <p>They are inactive before physical abuse</p> Signup and view all the answers

    What was a significant finding in the study carried out by Surette et al. (1990)?

    <p>Purification of nucleoside phosphorylase from bacteria in spoiled cod</p> Signup and view all the answers

    What is significantly impacted by temperature changes in the range of 0 to 25°C?

    <p>Microbiological growth</p> Signup and view all the answers

    Which temperature condition results in minimal growth for many bacteria?

    <p>At 0°C</p> Signup and view all the answers

    What is the primary reason for extending the shelf life of fish products?

    <p>Minimizing microbial activity</p> Signup and view all the answers

    What is the impact of storing fresh fish in ice at 0°C?

    <p>Decreases the relative rate of spoilage</p> Signup and view all the answers

    What does the relative rate of spoilage (RRS) depict with regard to fish storage?

    <p>Microbial growth as a function of temperature</p> Signup and view all the answers

    At which temperature do many bacteria begin to have significantly reduced growth rates?

    <p>Below 10°C</p> Signup and view all the answers

    Why do psychrotrophic organisms show slow growth at low temperatures?

    <p>They enter a lag phase near 0°C</p> Signup and view all the answers

    In industrialized countries, how is fresh fish typically preserved at low temperatures?

    <p>Storing in ice at 0°C</p> Signup and view all the answers

    What effect does temperature have on the relative rate of spoilage (RRS) of seafood products?

    <p>RRS increases with rising storage temperatures.</p> Signup and view all the answers

    Which microflora are primarily responsible for seafood spoilage at low temperatures (0-5°C)?

    <p>Shewanella putrefaciens and Aeromonas spp.</p> Signup and view all the answers

    Which spoilage model is suggested by Ratkowsky et al. for sub-optimal temperatures?

    <p>2-parameter square root model.</p> Signup and view all the answers

    What is the predicted relative rate of spoilage (RRS) for typical tropical fish stored at 25°C compared to 0°C?

    <p>Approximately 25 times higher.</p> Signup and view all the answers

    What is the effect of temperature history in fish storage as indicated by temperature loggers?

    <p>It allows estimation of microbiological growth from safety models.</p> Signup and view all the answers

    What happens to the RRS of packed fresh fish and superchilled fresh fish products?

    <p>They have a lower RRS than whole fresh fish.</p> Signup and view all the answers

    Why was the Arrhenius Equation deemed inaccurate for predicting spoilage rates?

    <p>It fails to measure microbial growth accurately.</p> Signup and view all the answers

    Which temperature range hosts the highest variety of spoilage species for fish?

    <p>15-30°C.</p> Signup and view all the answers

    What cumulative effect does temperature have on seafood effectively predicted by spoilage models?

    <p>It predicts shelf life based on variable temperatures.</p> Signup and view all the answers

    What is the theoretical minimum temperature for growth of psychrotrophic bacteria according to research?

    <p>263 Kelvin.</p> Signup and view all the answers

    Which factor limits the practical usage of electronic time/temperature function integrators for predicting RRS?

    <p>High cost of the devices.</p> Signup and view all the answers

    Which of the following spoilage models incorporates a relative rate concept?

    <p>Temperature spoilage model (Equation 6.c).</p> Signup and view all the answers

    Which organism primarily causes spoilage at elevated temperatures (15-30°C)?

    <p>Different species of Vibrionaceae.</p> Signup and view all the answers

    What negative effect has been observed with superchilling certain fish species?

    <p>It leads to unsatisfactory appearance and texture.</p> Signup and view all the answers

    How does the temperature affect the percentage of frozen water in superchilled fish?

    <p>Frozen water percentage is highly temperature-dependent.</p> Signup and view all the answers

    What conclusion can be drawn about the importance of hygiene during onboard handling of fish?

    <p>Hygiene has a minor impact compared to effective chilling.</p> Signup and view all the answers

    What was observed regarding the organoleptic quality of fish after different handling procedures?

    <p>Quality differences only appeared after the first week of storage.</p> Signup and view all the answers

    What factor significantly affects the shelf life of superchilled shrimp compared to cod?

    <p>The species-specific reactions to temperature.</p> Signup and view all the answers

    Which storage temperature led to increased drip loss in superchilled cod?

    <p>-3°C</p> Signup and view all the answers

    What has been suggested regarding the construction of fish boxes for chilling purposes?

    <p>Boxes should allow drainage of melt-water for effective chilling.</p> Signup and view all the answers

    Which method has been considered for prolonging storage life by reducing bacterial counts?

    <p>Radioactive irradiation.</p> Signup and view all the answers

    What relationship was established between bacterial contamination and fish storage life?

    <p>Less contaminated fish have a longer storage life.</p> Signup and view all the answers

    What effect does lowering the pH have on muscle proteins in fish?

    <p>It decreases water-holding capacity</p> Signup and view all the answers

    What was the observed impact of the superchilling technique on mackerel storage at -3°C?

    <p>It improved both freshness and shelf life.</p> Signup and view all the answers

    What is the primary impact of temperature on the shelf life of fish products?

    <p>Temperature affects the relative rate of spoilage linearly.</p> Signup and view all the answers

    Which of the following statements is true regarding the effects of RSW storage?

    <p>It can cause a salty taste in some species.</p> Signup and view all the answers

    Which fish products are noted as having increased drip loss when stored in high CO2 concentrations?

    <p>Cod fillets and salmon</p> Signup and view all the answers

    What is a significant negative effect of storing fish in 100% CO2?

    <p>Decreased textural quality</p> Signup and view all the answers

    Why is it challenging to unload fish when heat exchanges are used on vessels?

    <p>There are complications with fish storage methods.</p> Signup and view all the answers

    Which factor does NOT influence the rate of spoilage in fish?

    <p>Ambient humidity</p> Signup and view all the answers

    How does the demerit point system relate to fish quality assessment?

    <p>It offers a quantitative description of quality change over time.</p> Signup and view all the answers

    What is a consequence of the ice crystals formed during superchilling in fish?

    <p>Formation of large ice crystals causing protein denaturation.</p> Signup and view all the answers

    How does the addition of CO2 to refrigerated seawater (RSW) influence the shelf life of pink shrimps?

    <p>Doubles shelf life compared to ice storage</p> Signup and view all the answers

    What has research indicated about the sensory quality of fish stored using superchilling methods?

    <p>Sensory quality can be improved but varies by species.</p> Signup and view all the answers

    What is the effect of exposure to high temperatures before chilling on white-fleshed fish?

    <p>It may cause rupture and gaping in the muscle tissue.</p> Signup and view all the answers

    What is a common problem associated with CO2 in RSW systems?

    <p>Corrosive effects on equipment</p> Signup and view all the answers

    What is superchilling in fish storage?

    <p>Keeping fish at temperatures between 0°C and -4°C.</p> Signup and view all the answers

    Which of the following bacteria is noted to exhibit increased toxin production in anaerobic conditions?

    <p>Clostridium botulinum</p> Signup and view all the answers

    Which equation is used to determine the shelf life of fish at different temperatures based on initial quality?

    <p>Equation 6.e</p> Signup and view all the answers

    What happens to fish that are not gutted before storage?

    <p>They can develop strong off-flavors</p> Signup and view all the answers

    What impact does CO2 have on the color of fish stored in high concentrations?

    <p>Causes color fading</p> Signup and view all the answers

    What is a common effect of lipid oxidation in fish?

    <p>Formation of rancid off-flavors.</p> Signup and view all the answers

    What was the suggestion made by Spencer and Baines regarding fish spoilage?

    <p>Initial product quality and storage temperature can be predicted.</p> Signup and view all the answers

    How does the production of TMA in fish products during MAP compare to traditional storage methods?

    <p>It is delayed by several days</p> Signup and view all the answers

    What role does the Frigido-system serve in fish storage?

    <p>It helps maintain sub-zero temperatures during storage.</p> Signup and view all the answers

    Why has modified atmosphere packaging (MAP) found less practical application with fish products compared to meats?

    <p>High costs and limited shelf life extensions</p> Signup and view all the answers

    What is primarily affected by CO2 levels in fish storage?

    <p>Color and texture</p> Signup and view all the answers

    Which temperature range is associated with the square root spoilage model?

    <p>0°C to -4°C</p> Signup and view all the answers

    What is a major consequence of delayed chilling for fatty fish?

    <p>Increased oxidation and reduced storage life.</p> Signup and view all the answers

    For which type of fish is the negative impact of CO2 on color and texture less critical?

    <p>Fish intended for meal production</p> Signup and view all the answers

    How does the storage system using refrigerated sea water (RSW) benefit fish storage?

    <p>By efficiently reducing fish cooling time.</p> Signup and view all the answers

    What is the best description of the overall effect of CO2 on fish stored in RSW?

    <p>Has both positive and negative impacts</p> Signup and view all the answers

    What common problem occurs when white-fleshed fish are not chilled properly?

    <p>Separation of muscle flakes and gaping.</p> Signup and view all the answers

    What is a consequence of the strong digestive enzymes present in fish prior to gutting?

    <p>Post-mortem autolysis and strong off-flavors</p> Signup and view all the answers

    What importance does initial product quality hold in temperature spoilage models?

    <p>It influences the predictions of shelf life at different temperatures.</p> Signup and view all the answers

    What is the approximate shelf life range of tropical marine fish when stored in ice?

    <p>12-35 days</p> Signup and view all the answers

    Which fish type has the longest shelf life according to the provided data?

    <p>Jobfish</p> Signup and view all the answers

    Which of the following species has a shelf life that exceeds 20 days when stored in ice?

    <p>Tropical catfish</p> Signup and view all the answers

    Which factor significantly influences the shelf life of fish in iced storage?

    <p>Bacterial growth rate</p> Signup and view all the answers

    Which species has the shortest shelf life in ice according to the data provided?

    <p>Summer herring</p> Signup and view all the answers

    What is the primary bacterial group responsible for spoilage in iced stored fish?

    <p>Pseudomonas spp.</p> Signup and view all the answers

    Which characteristic is used to differentiate spoilage between temperate and tropical fish?

    <p>Bacterial involvement</p> Signup and view all the answers

    Which marine fish species can last between 21 and 26 days in iced storage?

    <p>Spadefish</p> Signup and view all the answers

    What role does pH play in the shelf life of fish?

    <p>Lower pH contributes to longer shelf life</p> Signup and view all the answers

    What common misconception may arise regarding the spoilage rates between tropical and temperate fish?

    <p>All tropical fish spoil slower</p> Signup and view all the answers

    What aspect of tropical fish spoilage has been proposed as having less impact than previously thought?

    <p>Bacterial contamination levels</p> Signup and view all the answers

    What is a notable biochemical characteristic of spoilage in Shewanella-dominated fish?

    <p>Production of TMA and H2S</p> Signup and view all the answers

    What is often observed about the shelf life of freshwater fish compared to marine species?

    <p>Freshwater fish often last longer in storage</p> Signup and view all the answers

    What conclusion did Lima dos Santos reach regarding the shelf life of temperate versus tropical fish?

    <p>Temperate fish have similar shelf lives to tropical fish</p> Signup and view all the answers

    What effect does high CO2 concentration have on microbial growth in food products?

    <p>It reduces microbial growth.</p> Signup and view all the answers

    Which method has been shown to effectively extend the shelf life of fish?

    <p>Modified atmosphere packaging with CO2</p> Signup and view all the answers

    What is a primary concern of using chlorinated water for washing fish?

    <p>It produces off-flavors in the fish meat.</p> Signup and view all the answers

    What types of microorganisms dominate the spoilage of vacuum packed (VP) meat products?

    <p>Lactic Acid Bacteria</p> Signup and view all the answers

    Why does modified atmosphere packaging (MAP) have limited effect on the shelf life of fresh fish?

    <p>Fish spoilage is primarily due to resistant microorganisms.</p> Signup and view all the answers

    What happens to the pH level of fish flesh stored in CO2 packed conditions?

    <p>It decreases by 0.2-0.3 units.</p> Signup and view all the answers

    Which of the following fish species is generally better suited for MAP storage?

    <p>Warmwater fish like swordfish</p> Signup and view all the answers

    What is the spoilage organism primarily responsible for packed cod spoilage?

    <p>Photobacterium phosphoreum</p> Signup and view all the answers

    What common reaction is caused by the metabolic activity of Photobacterium phosphoreum in spoiled fish?

    <p>High levels of TMA without extensive H2S</p> Signup and view all the answers

    How does the spoilage microflora differ between meat and fish?

    <p>Fish spoilage involves more aerobic Gram-negative organisms.</p> Signup and view all the answers

    What is the primary reason that washing fish in clean seawater is conducted?

    <p>To remove visible blood and dirt.</p> Signup and view all the answers

    What is a disadvantage of using antibiotics in fish storage methods?

    <p>It raises public health concerns.</p> Signup and view all the answers

    What is the characteristic growth response of Shewanella putrefaciens in CO2-rich environments?

    <p>Strong inhibition of growth.</p> Signup and view all the answers

    Which factor contributes to the relatively short shelf lives of aquatic products compared to meat?

    <p>Non-microbial spoilage reactions.</p> Signup and view all the answers

    What primarily contributes to the longer shelf life of tropical fish according to the findings?

    <p>Lower number of psychrotrophic bacteria</p> Signup and view all the answers

    How does the bacterial growth profile of tropical fish differ from that of temperate water fish?

    <p>Tropical fish exhibit a prolonged lag phase.</p> Signup and view all the answers

    What is the significance of psychrotrophic organisms on iced tropical fish?

    <p>Their growth rate is often slower.</p> Signup and view all the answers

    Which group of bacteria is often found dominating tropical fish caught in warm waters?

    <p>Gram-negative rod-shaped bacteria</p> Signup and view all the answers

    What can cause an off-flavour described as 'mineral oil' in certain fish?

    <p>Consumption of planktonic mollusc</p> Signup and view all the answers

    Which compound is primarily responsible for the muddy-earthy taint in freshwater fish?

    <p>Geosmin</p> Signup and view all the answers

    What factor has a significant impact on the shelf life of fish according to the findings?

    <p>Physiology of bacterial flora</p> Signup and view all the answers

    What happens to the bacterial composition in areas with fluctuating temperatures, according to the findings?

    <p>The taxonomic composition remains unchanged.</p> Signup and view all the answers

    What is the cause of the iodine-like flavour found in some marine fish?

    <p>Volatile bromophenolic compounds</p> Signup and view all the answers

    Which type of bacteria has shown to grow more quickly at lower temperatures if pre-cultured at moderate temperatures?

    <p>Aeromonas spp.</p> Signup and view all the answers

    Which of the following is a plausible reason for fish spoilage at rates similar to temperate water fish?

    <p>Not fully explained by current hypotheses</p> Signup and view all the answers

    What is a common reason for off-flavours in fish related to oil spills?

    <p>Presence of aromatic hydrocarbons</p> Signup and view all the answers

    During which specific condition can a significant bacterial lag phase for tropical fish occur?

    <p>When stored in ice</p> Signup and view all the answers

    Which of the following bacteria is known to predominantly thrive on iced cod?

    <p>Pseudomonas spp.</p> Signup and view all the answers

    What is a key characteristic of the bacteria found in Narragansett Bay over a 2-year period?

    <p>Stable taxonomic composition despite temperature changes</p> Signup and view all the answers

    What is one reason why small- and medium-sized fatty fish are not typically gutted immediately after being caught?

    <p>Discoloration and rancidity issues arise.</p> Signup and view all the answers

    How does gutting affect the quality of lean fish like cod?

    <p>Quality loss occurs if not gutted.</p> Signup and view all the answers

    Which type of fish is reported to be unaffected by whether it is gutted or ungutted?

    <p>South American hake</p> Signup and view all the answers

    What has been found to contribute to the occurrence of belly-burst in ungutted fish?

    <p>Lower strength of connective tissue.</p> Signup and view all the answers

    Which factor does NOT influence the spoilage rate of fish?

    <p>Weather conditions during catch.</p> Signup and view all the answers

    What is a primary characteristic that typically affects the shelf life of fatty fish compared to lean fish?

    <p>Fat content.</p> Signup and view all the answers

    What is the observed effect on the pH level of well-fed fish post mortem?

    <p>It is lower than in starved fish.</p> Signup and view all the answers

    Which type of fish is generally associated with a longer shelf life when stored in ice?

    <p>Flat fish.</p> Signup and view all the answers

    What specific issue is specifically linked to rough handling of fish post-catch?

    <p>Faster spoilage rates.</p> Signup and view all the answers

    In terms of spoilage rates, how do larger fish generally compare to smaller fish?

    <p>They spoil more slowly.</p> Signup and view all the answers

    Which of the following characteristics is most commonly associated with fatty pelagic fish that affects their spoilage rate?

    <p>Thin skin.</p> Signup and view all the answers

    What is the effect of the type of feed ingested by fish on their quality?

    <p>It may play a role in belly-burst phenomena.</p> Signup and view all the answers

    What is a common misconception about the influence of fish species on spoilage rates?

    <p>All species spoil at the same rate.</p> Signup and view all the answers

    Which factor is NOT considered when determining the advantages of gutting fish?

    <p>Color of the fish.</p> Signup and view all the answers

    What is the primary effect of chill storage temperatures on microbiological activity?

    <p>Microbiological activity is more significantly influenced by temperature changes than enzymatic activity.</p> Signup and view all the answers

    At which temperature do many bacteria begin to show an inability to grow?

    <p>Below 10°C</p> Signup and view all the answers

    How does the growth rate of Shewanella Putrefaciens at 0°C compare to its optimum growth temperature?

    <p>It is significantly lower than the optimum growth rate.</p> Signup and view all the answers

    What is the typical storage temperature range for extending the shelf life of fish products?

    <p>0-25°C</p> Signup and view all the answers

    What is the concept of relative rate of spoilage (RRS) in relation to fish storage?

    <p>A measure of how quickly fish spoil at varying temperatures.</p> Signup and view all the answers

    What is the impact of low-temperature storage on the shelf life of fish products?

    <p>It markedly extends shelf life.</p> Signup and view all the answers

    Which of the following best describes the lag phase of psychrotrophic organisms at low temperatures?

    <p>They grow slowly and may experience prolonged lag phases.</p> Signup and view all the answers

    Which statement is true regarding the relationship between temperature and microbiological growth?

    <p>Temperature changes significantly affect microbial growth more than enzymatic activity.</p> Signup and view all the answers

    What is the shelf life of crab claws stored at 10°C according to the provided data?

    <p>1.8 days</p> Signup and view all the answers

    What growth characteristic of microorganisms is suggested when using the square root spoilage model?

    <p>Relative growth rate similar to spoilage rate</p> Signup and view all the answers

    Which of the following fish is noted to have a significantly longer shelf life at 0°C compared to others?

    <p>Sea bream</p> Signup and view all the answers

    What is the Arrhenius Equation used to describe?

    <p>The effect of temperature on chemical reaction rates</p> Signup and view all the answers

    What type of bacteria is primarily responsible for spoilage at low temperatures (0-5°C)?

    <p>Shewanella putrefaciens</p> Signup and view all the answers

    Which spoilage model is mentioned as giving good estimates of temperature effects on bacteria?

    <p>2-parameter square root model</p> Signup and view all the answers

    Which spoilage factor is NOT accounted for by Equation 6.c?

    <p>Changes in spoilage microflora</p> Signup and view all the answers

    Which model allows prediction of the effect of variable temperatures on product keepability?

    <p>Time/temperature function integrator model</p> Signup and view all the answers

    What is the primary limitation of the electronic time/temperature function integrator?

    <p>High price</p> Signup and view all the answers

    How does the relative rate of spoilage for tropical fish compare to that of fish stored at lower temperatures?

    <p>Is about 25 times higher</p> Signup and view all the answers

    What is the theorized minimum temperature for microbial growth according to research on psychrotrophic bacteria?

    <p>263 Kelvin</p> Signup and view all the answers

    What is the effect of temperature on seafood spoilage described as?

    <p>An S-shaped general spoilage curve</p> Signup and view all the answers

    What historical research influenced the understanding of spoilage rates and temperature effects?

    <p>Research by Spencer and Baines</p> Signup and view all the answers

    What method has been rejected due to public health concerns for treating fish?

    <p>Antibiotic treatment incorporated in ice</p> Signup and view all the answers

    Which treatment method has shown success in extending the shelf life of fish?

    <p>CO2 treatment in chilled seawater</p> Signup and view all the answers

    What is the effect of chlorine when used for washing fish?

    <p>It creates off-flavors due to high concentrations.</p> Signup and view all the answers

    Which packaging method has the least increase in shelf life for fresh fish?

    <p>Modified atmosphere packaging</p> Signup and view all the answers

    What organisms are primarily responsible for spoilage of packed meat under anaerobic conditions?

    <p>Gram-positive organisms</p> Signup and view all the answers

    What key factor distinguishes spoilage in packed fish compared to packed meat?

    <p>Dominance of Gram-negative organisms</p> Signup and view all the answers

    Which Gram-negative organism is associated with spoilage of packed cod?

    <p>Photobacterium phosphoreum</p> Signup and view all the answers

    What effect does CO2 have on Shewanella putrefaciens in packed fish?

    <p>It inhibits their growth significantly.</p> Signup and view all the answers

    What effect does increased CO2 concentration have on the water-holding capacity of muscle proteins?

    <p>It decreases water-holding capacity.</p> Signup and view all the answers

    Which factor contributes to the relatively short shelf life of warmwater fish compared to other meat products?

    <p>Limited effect of vacuum packaging</p> Signup and view all the answers

    Which fish species showed no significant increase in drip loss when stored in high CO2 concentrations?

    <p>Red snapper</p> Signup and view all the answers

    What is a non-microbial factor that might influence spoilage in packed fish?

    <p>Chemical reactions occurring at low bacterial levels</p> Signup and view all the answers

    How does storage in RSW + CO2 influence the shelf life of pink shrimp compared to ice storage?

    <p>Shelf life can be more than doubled.</p> Signup and view all the answers

    What negative effect can result from the addition of CO2 to RSW systems?

    <p>Altered fish texture.</p> Signup and view all the answers

    How does CO2 affect the pH of MAP fish during storage?

    <p>It decreases pH by about 0.2-0.3 units.</p> Signup and view all the answers

    What is a common outcome of the spoilage pattern in packed cod?

    <p>High levels of TMA with little H2S development.</p> Signup and view all the answers

    What does CO2 do to the pH of seawater, and what is the impact on enzymatic reactions?

    <p>Decreases pH, inhibiting enzymatic reactions.</p> Signup and view all the answers

    What characteristic of Photobacterium phosphoreum affects cod shelf life?

    <p>It is resistant to CO2 concentrations.</p> Signup and view all the answers

    What quality issue has been observed in whole fish stored in high CO2 concentrations?

    <p>Altered color of belly flaps.</p> Signup and view all the answers

    What is a significant factor that can lead to inaccurate shelf life predictions for fish products?

    <p>Initial product quality</p> Signup and view all the answers

    What effect does MAP (Modified Atmosphere Packaging) have on seafood compared to meat products?

    <p>Less effective shelf life extension.</p> Signup and view all the answers

    Which bacteria's toxin production may be increased due to anaerobic conditions in packed fish?

    <p>Clostridium botulinum</p> Signup and view all the answers

    Which model predicts the shelf life of fish at different temperatures based on the relative rate concept?

    <p>Square root spoilage model</p> Signup and view all the answers

    Which fish species may become unsuitable for canning due to CO2 dissolving in the flesh?

    <p>Mackerel</p> Signup and view all the answers

    How does rapid chilling affect the quality of fatty fish?

    <p>It reduces storage life.</p> Signup and view all the answers

    What negative effect has been observed in cod stored at -2°C compared to those stored at 0°C?

    <p>Deterioration in appearance</p> Signup and view all the answers

    What is a significant drawback of RSW storage for some fish species?

    <p>Acquisition of a salty taste</p> Signup and view all the answers

    What is a possible consequence of not gutting fish before storage?

    <p>Increased risk of off-flavors due to autolysis.</p> Signup and view all the answers

    What is the relationship between storage temperature and relative rate of spoilage for tropical fish?

    <p>Linear relationship</p> Signup and view all the answers

    What impact does the delay before chilling have on fish quality?

    <p>Negative impact if above certain temperatures</p> Signup and view all the answers

    What is one of the main disadvantages of using MAP for retail fish products?

    <p>It can be expensive and not practical.</p> Signup and view all the answers

    Which factor contributes to the increased drip loss in superchilled fish?

    <p>Protein denaturation</p> Signup and view all the answers

    What was the observed effect of superchilling on shrimp from Pakistan?

    <p>Increased shelf life compared to ice storage</p> Signup and view all the answers

    Which equation is suggested for predicting the rate of change in quality scores at different temperatures?

    <p>Equation 6.c</p> Signup and view all the answers

    Which type of fish was found to have improved attributes such as color and texture when stored in RSW + CO2?

    <p>Pink shrimps</p> Signup and view all the answers

    Which is a required material in RSW + CO2 systems due to the corrosive nature of CO2 acidifying seawater?

    <p>Inert materials</p> Signup and view all the answers

    What was the impact of hygiene during the initial week of storage according to the experiments conducted?

    <p>No noticeable difference in organoleptic quality</p> Signup and view all the answers

    What storage technique can be used to extend the shelf life of various fish and shellfish?

    <p>Superchilling</p> Signup and view all the answers

    What is a crucial factor in the demerit point system regarding fish quality?

    <p>It provides a direct relationship between quality scores and storage time.</p> Signup and view all the answers

    How does bacterial activity usually affect fish quality during storage?

    <p>It becomes important only in later stages</p> Signup and view all the answers

    What phenomenon occurs when white-fleshed fish enter rigor mortis at high temperatures?

    <p>Separation of flakes in fillets</p> Signup and view all the answers

    What design consideration for fish boxes can improve chilling efficiency?

    <p>Allowing drainage of melt-water</p> Signup and view all the answers

    Which method has been found to prolong storage life but is considered costly and often unacceptable?

    <p>Radioactive irradiation</p> Signup and view all the answers

    What system allows reduction of the ice to fish ratio in storage and improves chilling efficacy?

    <p>Frigido-system</p> Signup and view all the answers

    Why is it important to maintain sub-zero temperatures in fishing vessels?

    <p>To reduce exposure to oxygen</p> Signup and view all the answers

    What is one of the main problems associated with superchilling cod and haddock?

    <p>Formation of large ice crystals</p> Signup and view all the answers

    What can be a consequence of insufficient chilling before transport?

    <p>Reduced fillet yield</p> Signup and view all the answers

    What temperature range was indicated for superchilling fish, regarding the water content in frozen state?

    <p>-1°C to -4°C</p> Signup and view all the answers

    Which fish species showed improvement in shelf life due to superchilling compared to ice storage?

    <p>Shrimp from Pakistan</p> Signup and view all the answers

    How does delayed icing affect the yield of fish fillets?

    <p>Decreases yield</p> Signup and view all the answers

    How does temperature influence the rate of spoilage in fish products?

    <p>Higher temperatures increase spoilage rates.</p> Signup and view all the answers

    What was the consequence of using dirty wooden boxes for fish storage?

    <p>Increased bacterial contamination</p> Signup and view all the answers

    What did experiments indicate about the effectiveness of strict hygienic measures in fish handling?

    <p>They have no impact on storage life</p> Signup and view all the answers

    What was one of the outcomes when comparing aseptic handling to normal handling of fish?

    <p>No significant difference in quality initially</p> Signup and view all the answers

    What is the primary reason small and medium-sized fatty fish are often not gutted immediately after being caught?

    <p>To prevent belly-burst and discoloration</p> Signup and view all the answers

    Which fish species is more likely to experience a significant reduction in quality if not gutted promptly?

    <p>Cod</p> Signup and view all the answers

    What environmental factor contributes to the faster spoilage rate of fish during periods of heavy feeding?

    <p>Lower post mortem pH levels</p> Signup and view all the answers

    What is a key factor affecting the shelf life of fish species under aerobic storage?

    <p>Size of the fish</p> Signup and view all the answers

    Which type of fish generally keeps longer under aerobic storage conditions?

    <p>Lean fish such as cod</p> Signup and view all the answers

    What happens to the texture of ungutted fish stored on ice compared to gutted fish?

    <p>It becomes tougher and less palatable</p> Signup and view all the answers

    Which off-odor is commonly associated with ungutted fish after a short period of storage?

    <p>Cabbage-like odor from the belly area</p> Signup and view all the answers

    What characterizes the spoilage rate when comparing bony fish with cartilaginous fish?

    <p>Cartilaginous fish spoil slower than bony fish</p> Signup and view all the answers

    What may influence the accelerated rancidity in fatty fish compared to lean fish?

    <p>Thin skin allowing faster spoilage</p> Signup and view all the answers

    Which factor plays a critical role in the quality of ungutted fish as per storage duration?

    <p>Type of feed ingested</p> Signup and view all the answers

    What is indicated by the term belly-burst in ungutted fish?

    <p>Swelling caused by bacterial growth</p> Signup and view all the answers

    What kind of change in pH occurs in well-fed fish post-mortem?

    <p>Decrease in pH resulting in weaker connective tissue</p> Signup and view all the answers

    What type of fish is South American hake considered in terms of gutting impact?

    <p>There is no observable difference between gutted and ungutted</p> Signup and view all the answers

    How does the shelf life of tropical freshwater fish compare to that of marine fish from temperate waters?

    <p>It is often longer than temperate marine fish.</p> Signup and view all the answers

    What bacterial species is suggested to dominate the spoilage process in iced tropical fish?

    <p>Pseudomonas spp.</p> Signup and view all the answers

    Which statement best describes the pH levels found in tropical fish species studied?

    <p>They have pH values between 6 and 7.</p> Signup and view all the answers

    What is a common misconception regarding the spoilage of tropical fish?

    <p>It is primarily caused by high bacterial counts.</p> Signup and view all the answers

    Which factor significantly influences the shelf life of the various fish species?

    <p>The water temperature from which they are sourced.</p> Signup and view all the answers

    Which of these fish species is noted for having a longer shelf life when stored in ice?

    <p>Jobfish</p> Signup and view all the answers

    What was the conclusion drawn by Lima dos Santos about the shelf life of temperate fish species?

    <p>Some maintain an extremely good shelf life.</p> Signup and view all the answers

    What is the iced shelf life range for marine fish from temperate waters?

    <p>2 to 21 days</p> Signup and view all the answers

    Which of the following fish types has a documented shelf life up to 35 days when stored in ice?

    <p>Jobfish</p> Signup and view all the answers

    Which factor is often cited for the slower spoilage rates observed in certain fish species?

    <p>Slower bacterial growth.</p> Signup and view all the answers

    What is a key difference in spoilage odors between tropical and temperate fish species?

    <p>Tropical fish spoilage is characterized by the absence of certain compounds.</p> Signup and view all the answers

    Which iced storage duration for tropical marine fish is commonly documented?

    <p>12-35 days</p> Signup and view all the answers

    What should be considered when comparing the shelf lives of tropical and temperate species?

    <p>The inconsistent definitions of tropical fish.</p> Signup and view all the answers

    Which of the following factors does NOT significantly affect the iced shelf life of fish species?

    <p>Fish size</p> Signup and view all the answers

    What is the primary reason attributed to the longer iced shelf life of tropical fish?

    <p>Lower number of psychrotrophs on tropical fish.</p> Signup and view all the answers

    What is a common characteristic of the bacterial flora found on tropical fish?

    <p>They typically show slower growth rates when stored on ice.</p> Signup and view all the answers

    How does the bacterial growth profile in Narragansett Bay relate to temperature fluctuations?

    <p>It remains constant despite temperature variations.</p> Signup and view all the answers

    What is a noted effect of pre-culturing fish spoilage bacteria at varying temperatures?

    <p>It can enhance growth rates at temperatures above freezing.</p> Signup and view all the answers

    What compound is responsible for the off-flavour known as 'mineral oil' in fish?

    <p>Dimethyl-b-propiothetin.</p> Signup and view all the answers

    Which factor is often linked to the off-flavours found in freshwater fish?

    <p>Consumption of specific planktonic organisms.</p> Signup and view all the answers

    What does geosmin contribute to in fish?

    <p>A muddy-earthy taint.</p> Signup and view all the answers

    What type of bacteria predominantly dominate tropical fish caught in warm waters?

    <p>Gram-negative rod-shaped bacteria.</p> Signup and view all the answers

    What negative aspect does an oil spill have on the quality of fish?

    <p>It causes off-flavours due to hydrocarbon accumulation.</p> Signup and view all the answers

    What was observed regarding the adaptation of tropical fish bacteria to chilled temperatures?

    <p>They require a lag phase before growth increases.</p> Signup and view all the answers

    Why might tropical fish have a slower growth of psychrotrophic bacteria compared to temperate fish?

    <p>They require longer adaptation periods to cold temperatures.</p> Signup and view all the answers

    Which process explains the off-flavour of fish that occurs due to certain feeding habits?

    <p>Chemical conversion within the fish.</p> Signup and view all the answers

    What is indicated by the generation times of fish spoilage bacteria when pre-cultured at different temperatures?

    <p>Pre-culture temperature influences growth speed at chill temperatures.</p> Signup and view all the answers

    Which factor is pointed out as varying among different fish species contributing to shelf life differences?

    <p>Physiology of the bacterial flora.</p> Signup and view all the answers

    Study Notes

    Fish Overview

    • Defined as aquatic vertebrates using gills for oxygen and fins with fin rays.
    • Major fish groups include cartilaginous fishes (sharks and rays) and bony fishes.
    • Over 20,000 fish species exist, with 58% found in marine environments.
    • Warm and temperate waters host around 8,000 species; only 225 species inhabit the open ocean.

    Taxonomy of Fish

    • Taxonomy classifies fish based on evolutionary relationships.
    • Scientific names follow binomial nomenclature, comprising genus and species (e.g., Delphinus delphis for common dolphin).
    • Common names can cause confusion due to regional variations.

    Classification by Characteristics

    • Fish are categorized into:
      • Cyclostomes: jawless fish (lampreys, slime-eels).
      • Chondrichthyes: cartilaginous fish (sharks, rays) with high urea content.
      • Teleostei: bony fish, further divided into:
        • Pelagic fish (fatty: herring, mackerel).
        • Demersal fish (lean: cod, haddock).

    Anatomy and Physiology

    Skeleton

    • Fish possess a vertebral column (backbone) and cranium.
    • Backbone is segmented into vertebrae with neural spines; ribs may vary from cartilaginous to bony.

    Muscle Anatomy and Function

    • Fish muscle lacks tendons, consists of parallel muscle cells (myotomes) connected by connective tissue (myocommata).
    • Dorsal and ventral muscle parts differ in fiber lengths and diameters.
    • Dark muscle, rich in lipids and myoglobin, is more prevalent in active pelagic species.

    Muscle Contraction

    • Contraction initiated by nervous impulses releasing Ca++, activating ATP-ase for muscle fiber contraction.
    • Dark muscle has higher energy; utilizes aerobic metabolism, while light muscle relies on anaerobic metabolism.

    Cardiovascular System

    • Fish heart operates on a single circulation system with two chambers.
    • Blood is pumped to gills for oxygenation, then distributed to the body.
    • Fish blood volume is 1.5-3.0% of body weight; primarily in internal organs.

    Bleeding and Handling

    • Bleeding fish post-capture can enhance fillet quality.
    • Recommendations vary on bleeding methods and times to limit discoloration and ensure quality.
    • Rough handling can lead to bruising and contamination of muscle tissues.

    Growth and Reproduction

    • Fish growth involves increasing muscle cell size, not quantity.
    • Sexual maturity is generally size-dependent, reaching earlier in males.
    • Gonad development takes energy, often occurring during low food intake.

    Chemical Composition

    • Varies by species, age, sex, environment, and season.
    • Key constituents include protein, lipid, and carbohydrate percentages, with fish typically lower in protein than isolated beef muscle.

    Sensory Changes in Fish

    • Sensory changes relate to appearance, odour, texture, and taste of fish, crucial for assessing freshness.
    • Rigor mortis begins immediately post-mortem, characterized by muscle stiffening, lasting for a day or more before resolving.
    • Fish muscle starts soft and limp post-death, then becomes hard and stiff due to rigor mortis, followed by a relaxed, non-elastic state.
    • Onset and duration of rigor mortis vary by species and are influenced by temperature, handling, and fish condition.
    • High temperatures accelerate rigor mortis, while some tropical fish show a faster onset at 0°C.
    • Stress and glycogen depletion at death hasten rigor mortis onset, with stunning methods significantly affecting timing.
    • Pre-rigor filleting yields better quality; rigor mortis leads to stiff muscle and poor filleting yields.
    • Post-rigor, fish flesh becomes firm and elastic, while cooking pre-rigor results in a soft texture.

    Evaluation of Freshness

    • Sensory evaluations consider appearance, texture, and odour, influenced by storage conditions.
    • Fish stored without ice spoil faster but have less visible change than those stored in ice.
    • Freshness changes can be categorized into four distinct phases:
      • Phase 1: Fresh fish has a sweet, delicate taste; optimal taste observed 2-3 days post-catch.
      • Phase 2: Loss of characteristic taste and odour; flesh still pleasant.
      • Phase 3: Signs of spoilage with unpleasant odours; texture deteriorates.
      • Phase 4: Fish is spoiled, exhibiting putrid characteristics.

    Autolytic Changes and Energy Production

    • Autolysis denotes "self-digestion," distinguishing between bacterial and enzymatic spoilage.
    • Lack of oxygen post-mortem disrupts normal energy production in muscles, relying on anaerobic pathways which are less efficient than aerobic respiration.
    • Depletion of ATP during rigor mortis results in stiff, inextensible muscle, complicating processing.
    • pH drops during post-mortem glycolysis, affecting muscle properties; drops range from 6.8 to lower levels depending on species.
    • Stress affects glycogen levels pre-capture, consequently altering post-mortem pH and quality.

    Autolysis and Nucleotide Catabolism

    • Rigor mortis onset correlates with a drop in ATP levels and degradation of ATP to AMP, IMP, and further derivatives.
    • Autolytic changes follow a predictable pattern after death, affecting perceived freshness quality.
    • Changes in ATP and its catabolites indicate spoilage but do not directly correlate with texture changes.
    • The freshness index (K value) is useful, but variability among species makes it unreliable for all marine fish.### Hx Determination and Fish Species
    • Hx determination is unlikely to be useful for species like swordfish and redfish due to their specific biological characteristics.

    Autolytic Changes in Fish

    • Physical handling accelerates autolytic changes in chilled fish, affecting edibility and filleting yields.
    • Sterile fillets show a greater breakdown rate of nucleotide catabolites compared to non-sterile cod, indicating that autolytic enzymes are compartmentalized.

    Importance of Handling Practices

    • Storing iced fish in boxes over 30 cm deep or allowing stacking can exacerbate autolysis.
    • Systems for moving fish must protect delicate tissues from physical damage.

    Nucleotide Catabolite Analysis

    • Rapid methods exist for determining individual nucleotide catabolites and freshness indices.

    Proteolytic Enzymes and Fish Quality

    • Autolytic proteolysis in fish leads to tissue softening, most notably in pelagic species like herring, especially during summer feeding, impacting commercial value.
    • Autolysis can promote bacterial growth, worsening spoilage and lowering fish quality.

    Cathepsins in Fish Autolysis

    • Cathepsins, acid proteases stored in lysosomes, become active post-mortem after physical stress, leading to significant tissue breakdown.
    • Cathepsin L is a major factor in muscle softening, with its activity correlated to the texture of fish muscle.

    Effects of Freezing on Autolysis

    • Freezing breaks cell membranes, releasing enzymes like cathepsins, enhancing autolysis and softening.
    • Studies show cathepsin L activity is higher in frozen/thawed tissues compared to fresh, influencing the muscle's texture.

    Calpains Role in Texture Changes

    • Calpains, calcium-activated proteases, significantly contribute to fish muscle autolysis, particularly at physiological pH levels.
    • Active at lower temperatures compared to mammalian counterparts, calpains contribute to texture softening during chilled storage.

    Collagenase Effects on Fish Texture

    • Collagenases weaken connective tissue in fish, leading to gaping in fillets and softening during storage.
    • The breakdown of type V collagen correlates with textural degradation of fish tissue.

    TMAO and Formaldehyde Production

    • TMAO, regulated by bacterial action and intrinsic enzymes, can be converted into dimethylamine and formaldehyde, leading to detrimental toughening of fish muscle.
    • Enzymes responsible for this reaction, especially in gadoid fishes, become active upon tissue disruption by freezing.

    Prevention Strategies for Autolytic Changes

    • Minimizing physical damage and maintaining low storage temperatures (< -30°C) can prevent toughening from autolytic actions.
    • Importance of adhering to proper handling practices before freezing to maintain fish quality.

    General Summary of Autolytic Changes in Fish

    • Both physical disruption and environmental conditions play critical roles in the rate and extent of autolytic changes in fish.
    • Key enzymes involved include glycolytic enzymes, autolytic enzymes for nucleotide breakdown, cathepsins, calpains, and collagenases, each with specific impacts on texture and quality.

    Sensory Changes in Fish

    • Sensory changes relate to appearance, odour, texture, and taste of fish, crucial for assessing freshness.
    • Rigor mortis begins immediately post-mortem, characterized by muscle stiffening, lasting for a day or more before resolving.
    • Fish muscle starts soft and limp post-death, then becomes hard and stiff due to rigor mortis, followed by a relaxed, non-elastic state.
    • Onset and duration of rigor mortis vary by species and are influenced by temperature, handling, and fish condition.
    • High temperatures accelerate rigor mortis, while some tropical fish show a faster onset at 0°C.
    • Stress and glycogen depletion at death hasten rigor mortis onset, with stunning methods significantly affecting timing.
    • Pre-rigor filleting yields better quality; rigor mortis leads to stiff muscle and poor filleting yields.
    • Post-rigor, fish flesh becomes firm and elastic, while cooking pre-rigor results in a soft texture.

    Evaluation of Freshness

    • Sensory evaluations consider appearance, texture, and odour, influenced by storage conditions.
    • Fish stored without ice spoil faster but have less visible change than those stored in ice.
    • Freshness changes can be categorized into four distinct phases:
      • Phase 1: Fresh fish has a sweet, delicate taste; optimal taste observed 2-3 days post-catch.
      • Phase 2: Loss of characteristic taste and odour; flesh still pleasant.
      • Phase 3: Signs of spoilage with unpleasant odours; texture deteriorates.
      • Phase 4: Fish is spoiled, exhibiting putrid characteristics.

    Autolytic Changes and Energy Production

    • Autolysis denotes "self-digestion," distinguishing between bacterial and enzymatic spoilage.
    • Lack of oxygen post-mortem disrupts normal energy production in muscles, relying on anaerobic pathways which are less efficient than aerobic respiration.
    • Depletion of ATP during rigor mortis results in stiff, inextensible muscle, complicating processing.
    • pH drops during post-mortem glycolysis, affecting muscle properties; drops range from 6.8 to lower levels depending on species.
    • Stress affects glycogen levels pre-capture, consequently altering post-mortem pH and quality.

    Autolysis and Nucleotide Catabolism

    • Rigor mortis onset correlates with a drop in ATP levels and degradation of ATP to AMP, IMP, and further derivatives.
    • Autolytic changes follow a predictable pattern after death, affecting perceived freshness quality.
    • Changes in ATP and its catabolites indicate spoilage but do not directly correlate with texture changes.
    • The freshness index (K value) is useful, but variability among species makes it unreliable for all marine fish.### Hx Determination and Fish Species
    • Hx determination is unlikely to be useful for species like swordfish and redfish due to their specific biological characteristics.

    Autolytic Changes in Fish

    • Physical handling accelerates autolytic changes in chilled fish, affecting edibility and filleting yields.
    • Sterile fillets show a greater breakdown rate of nucleotide catabolites compared to non-sterile cod, indicating that autolytic enzymes are compartmentalized.

    Importance of Handling Practices

    • Storing iced fish in boxes over 30 cm deep or allowing stacking can exacerbate autolysis.
    • Systems for moving fish must protect delicate tissues from physical damage.

    Nucleotide Catabolite Analysis

    • Rapid methods exist for determining individual nucleotide catabolites and freshness indices.

    Proteolytic Enzymes and Fish Quality

    • Autolytic proteolysis in fish leads to tissue softening, most notably in pelagic species like herring, especially during summer feeding, impacting commercial value.
    • Autolysis can promote bacterial growth, worsening spoilage and lowering fish quality.

    Cathepsins in Fish Autolysis

    • Cathepsins, acid proteases stored in lysosomes, become active post-mortem after physical stress, leading to significant tissue breakdown.
    • Cathepsin L is a major factor in muscle softening, with its activity correlated to the texture of fish muscle.

    Effects of Freezing on Autolysis

    • Freezing breaks cell membranes, releasing enzymes like cathepsins, enhancing autolysis and softening.
    • Studies show cathepsin L activity is higher in frozen/thawed tissues compared to fresh, influencing the muscle's texture.

    Calpains Role in Texture Changes

    • Calpains, calcium-activated proteases, significantly contribute to fish muscle autolysis, particularly at physiological pH levels.
    • Active at lower temperatures compared to mammalian counterparts, calpains contribute to texture softening during chilled storage.

    Collagenase Effects on Fish Texture

    • Collagenases weaken connective tissue in fish, leading to gaping in fillets and softening during storage.
    • The breakdown of type V collagen correlates with textural degradation of fish tissue.

    TMAO and Formaldehyde Production

    • TMAO, regulated by bacterial action and intrinsic enzymes, can be converted into dimethylamine and formaldehyde, leading to detrimental toughening of fish muscle.
    • Enzymes responsible for this reaction, especially in gadoid fishes, become active upon tissue disruption by freezing.

    Prevention Strategies for Autolytic Changes

    • Minimizing physical damage and maintaining low storage temperatures (< -30°C) can prevent toughening from autolytic actions.
    • Importance of adhering to proper handling practices before freezing to maintain fish quality.

    General Summary of Autolytic Changes in Fish

    • Both physical disruption and environmental conditions play critical roles in the rate and extent of autolytic changes in fish.
    • Key enzymes involved include glycolytic enzymes, autolytic enzymes for nucleotide breakdown, cathepsins, calpains, and collagenases, each with specific impacts on texture and quality.

    Effect of Storage Temperature

    • Microbial vs. Enzymatic Activity: Temperature between 0-25°C significantly impacts microbial growth more than enzymatic activity; many bacteria, including Shewanella putrefaciens, grow poorly below 10°C, with growth rates drastically reduced at 0°C.
    • Extended Shelf Life: Low storage temperatures extend the shelf life of fresh fish products due to reduced microbial spoilage.
    • Relative Rate of Spoilage (RRS): RRS is a crucial measure expressed for various seafood stored at different temperatures, showing drastic differences in shelf life at 0°C, 5°C, and 10°C. For example, crab has a shelf life of 10.1 days at 0°C but only 2.6 days at 10°C.
    • Spoilage Models: The relationship between temperature and RRS is represented by an S-shaped spoilage curve, confirming earlier research findings and allowing predictions of spoilage based on temperature changes.
    • Temperature Influence on Reactions: While the Arrhenius Equation describes temperature effects on chemical reactions, it isn't completely accurate for microbial growth over various temperatures.
    • Psychrotrophic Bacteria: Preferred survival temperatures for psychrotrophic bacteria yield a theoretical minimum growth temperature (Tmin), around -10°C for some species, underscoring the effectiveness of optimized storage models.

    Superchilling and Partial Freezing

    • Superchilling Defined: Storing fish at temperatures from 0°C to -4°C is termed superchilling, which significantly prolongs shelf life compared to regular icing (e.g., shelf life at -3°C can exceed that at 0°C).
    • Frigido-system Technology: Developed in the 1960s, this technology maintains sub-zero temperatures in fish holds, reducing fish:ice ratios and enhancing chilling efficacy.
    • Negative Effects on Freshness: Some fish may lose quality due to superchilling, with increased drip loss and inferior texture characteristics compared to ice storage, highlighting species variability in response to superchilling.
    • Liquid Refrigerated Sea Water (RSW): RSW reduces oxygen exposure and facilitates quicker chilling compared to traditional ice methods, although it may impart a salty taste to some fish species.

    Importance of Hygiene During Handling

    • Onboard Hygienic Practices: Research indicates that while proper hygiene during fish handling can reduce bacterial contamination, strict measures are less critical compared to rapid chilling methods.
    • Bacterial Growth Factors: Initial bacterial levels influence storage life more significantly in the latter stages, with high contamination leading to reduced shelf life post the first week.
    • Handling Logistics: Fish storage boxes should permit melt-water drainage to enhance chilling efficiency without significantly increasing contamination risks.

    Microbial Control Methods

    • Limitations of Traditional Methods: Techniques like irradiation or antibiotics for bacterial control are often rejected due to cost or health concerns.
    • Effective Alternatives: CO2 treatment and chlorinated water washing are promising methods for bacterial reduction, improving overall product quality during handling and distribution.

    Conclusion and Future Implications

    • Superchilling as a Viable Option: While superchilling can improve shelf life significantly, the potential drawbacks for some species necessitate targeted application.
    • Technological Advances: Continued development of predictive models and monitoring technologies such as temperature loggers will enhance seafood quality control, ensuring safer consumption practices.### Handling and Storage of Fish
    • Chlorine can prolong storage life but creates off-flavors in fish.
    • Newly caught fish should be washed in clean seawater to remove visible blood and dirt, with no significant impact on bacterial count or storage life.

    Impact of Anaerobic Conditions and Carbon Dioxide (CO2)

    • High CO2 concentrations inhibit microbial growth, thereby extending shelf life where spoilage is microbially driven.
    • Technologies like vacuum packaging (VP) and modified atmosphere packaging (MAP) are effective, particularly for meats, but provide minimal shelf life extension for fish.

    Shelf Life Comparison

    • Shelf life (in weeks) at 0.0 - 4.0°C:
      • Lean fish:
        • Air: 1-2,
        • VP: 1-2,
        • MAP: 1-3
      • Fatty fish:
        • Air: 1-2,
        • VP: 1-2,
        • MAP: 1-3
    • Meat products show significantly longer shelf lives under similar conditions compared to fish products.

    Microbial Spoilage

    • Aerobic spoilage in meats is caused primarily by Pseudomonas spp., which are inhibited in anaerobic conditions, shifting spoilage to Gram-positive lactic acid bacteria.
    • Fish spoil primarily from Shewanella putrefaciens under aerobic conditions, countered by high CO2 levels in packaged fish.
    • Photobacterium phosphoreum, a Gram-negative organism, is identified as the primary spoilage microorganism in vacuum-packaged cod, growing well under anaerobic conditions.

    Non-Microbial Spoilage Reactions

    • Increased CO2 causes pH decrease (0.2-0.3 units), affecting muscle protein water-holding capacity, leading to higher drip loss in some fish.
    • Sensory quality of fish in high CO2 environments may be compromised, particularly at 100% CO2, while up to 60% CO2 shows minimal texture impact on cod.

    Refrigerated Seawater (RSW) Systems

    • RSW + CO2 improves the shelf life of certain fish products, compared to ice storage.
    • CO2 can prolong the shelf life of pink shrimp significantly, but may adversely affect color and texture in other species like mackerel.

    Factors Affecting Quality and Storage Life

    • Evisceration generally enhances quality and shelf life, particularly in lean species like cod, where ungutted fish show rapid quality degradation.
    • Gutting increases exposure to air, raising oxidation risks, leading to discoloration.

    Species-Specific Insights

    • Fatty fish like herring and sardines are often stored ungutted due to challenges with discoloration and rancidity.
    • Quality of perishable fish species is affected by species, fishing grounds, fishing methods, and seasonal factors.

    Intrinsic Factors of Spoilage

    • Spoilage is slower in larger fish, flat fish tend to keep better, and lean fish have longer storage capabilities than fatty species.
    • Factors such as rough handling lead to increased spoilage rates due to physical damage increasing bacterial access.

    Bacterial Growth and Spoilage Rate

    • Post-mortem pH and fat content directly influence spoilage rates; higher pH and fat content generally lead to faster spoilage.
    • Bacterial growth rates differ among species, impacting overall shelf life.

    Environmental and Temperature Influences

    • Cold-water species generally exhibit shorter iced shelf lives than tropical species, which have been reported to outperform in storage longevity.
    • Historical studies have shown some tropical fish maintain freshness in ice for 20-30 days, indicating a significant difference in spoilage dynamics between warm and cold-water species.### Fish Shelf Life Comparison
    • Fish from warm waters generally have longer shelf lives compared to those from temperate waters.
    • Freshwater fish species exhibit longer shelf lives than marine species.
    • Tropical marine fish can last 12-35 days when stored in ice, whereas temperate marine fish last 2-21 days.
    • Temperate freshwater fish shelf life ranges from 9 to 20 days.

    Factors Affecting Fish Spoilage

    • Prolonged shelf life in tropical fish may be related to lower levels of Trimethylamine (TMA) and Total Volatile Nitrogen (TVN) during storage.
    • Pseudomonas spp. are often responsible for spoilage in tropical fish, differing from Shewanella spp. which produce TMA and sulfides.
    • The absence of TMA and TVN in some tropical fish suggests spoilage mechanisms that might not involve typical bacteria.
    • Tropical fish exhibit a lag phase of 1-2 weeks before bacterial growth resumes when stored in ice.

    Bacterial Flora Influences

    • Gram-negative bacteria such as Pseudomonas and Acinetobacter are prevalent in tropical fish, potentially influencing spoilage rates.
    • Studies show high percentages (40-90%) of tropical fish bacteria can grow at chill temperatures (7°C).
    • Tropical fish tend to have slower spoilage rates compared to temperate fish, supporting the adaptation hypothesis.

    Physiological Differences

    • pH levels of tropical fish measured between 6-7, lower than some temperate species, may contribute to longer shelf life.
    • The thick skin of tropical fish might also play a role in preservation, though further research on skin properties is needed.

    Off-Flavours in Fish

    • Off-flavours in fish can arise from diet, leading to taints such as "mineral oil" from planktonic molluscs.
    • Bitter tastes in herring can be due to larvae from Mytilus spp., while muddy-earthy taints in freshwater fish stem from geosmin and 2-methylisoborneol.
    • Iodine-like flavours may indicate the presence of volatile bromophenolic compounds derived from marine organisms.
    • Environmental factors, such as oil spills, can cause oil taint due to soluble hydrocarbon compounds that accumulate in fish flesh.

    Storage and Handling Practices

    • Proper handling, such as rapid chilling of ungutted fish, is crucial for maintaining quality.
    • The type of bacterial flora and environmental conditions before and after catch impact fish longevity and quality.

    Effect of Storage Temperature

    • Microbial vs. Enzymatic Activity: Temperature between 0-25°C significantly impacts microbial growth more than enzymatic activity; many bacteria, including Shewanella putrefaciens, grow poorly below 10°C, with growth rates drastically reduced at 0°C.
    • Extended Shelf Life: Low storage temperatures extend the shelf life of fresh fish products due to reduced microbial spoilage.
    • Relative Rate of Spoilage (RRS): RRS is a crucial measure expressed for various seafood stored at different temperatures, showing drastic differences in shelf life at 0°C, 5°C, and 10°C. For example, crab has a shelf life of 10.1 days at 0°C but only 2.6 days at 10°C.
    • Spoilage Models: The relationship between temperature and RRS is represented by an S-shaped spoilage curve, confirming earlier research findings and allowing predictions of spoilage based on temperature changes.
    • Temperature Influence on Reactions: While the Arrhenius Equation describes temperature effects on chemical reactions, it isn't completely accurate for microbial growth over various temperatures.
    • Psychrotrophic Bacteria: Preferred survival temperatures for psychrotrophic bacteria yield a theoretical minimum growth temperature (Tmin), around -10°C for some species, underscoring the effectiveness of optimized storage models.

    Superchilling and Partial Freezing

    • Superchilling Defined: Storing fish at temperatures from 0°C to -4°C is termed superchilling, which significantly prolongs shelf life compared to regular icing (e.g., shelf life at -3°C can exceed that at 0°C).
    • Frigido-system Technology: Developed in the 1960s, this technology maintains sub-zero temperatures in fish holds, reducing fish:ice ratios and enhancing chilling efficacy.
    • Negative Effects on Freshness: Some fish may lose quality due to superchilling, with increased drip loss and inferior texture characteristics compared to ice storage, highlighting species variability in response to superchilling.
    • Liquid Refrigerated Sea Water (RSW): RSW reduces oxygen exposure and facilitates quicker chilling compared to traditional ice methods, although it may impart a salty taste to some fish species.

    Importance of Hygiene During Handling

    • Onboard Hygienic Practices: Research indicates that while proper hygiene during fish handling can reduce bacterial contamination, strict measures are less critical compared to rapid chilling methods.
    • Bacterial Growth Factors: Initial bacterial levels influence storage life more significantly in the latter stages, with high contamination leading to reduced shelf life post the first week.
    • Handling Logistics: Fish storage boxes should permit melt-water drainage to enhance chilling efficiency without significantly increasing contamination risks.

    Microbial Control Methods

    • Limitations of Traditional Methods: Techniques like irradiation or antibiotics for bacterial control are often rejected due to cost or health concerns.
    • Effective Alternatives: CO2 treatment and chlorinated water washing are promising methods for bacterial reduction, improving overall product quality during handling and distribution.

    Conclusion and Future Implications

    • Superchilling as a Viable Option: While superchilling can improve shelf life significantly, the potential drawbacks for some species necessitate targeted application.
    • Technological Advances: Continued development of predictive models and monitoring technologies such as temperature loggers will enhance seafood quality control, ensuring safer consumption practices.### Handling and Storage of Fish
    • Chlorine can prolong storage life but creates off-flavors in fish.
    • Newly caught fish should be washed in clean seawater to remove visible blood and dirt, with no significant impact on bacterial count or storage life.

    Impact of Anaerobic Conditions and Carbon Dioxide (CO2)

    • High CO2 concentrations inhibit microbial growth, thereby extending shelf life where spoilage is microbially driven.
    • Technologies like vacuum packaging (VP) and modified atmosphere packaging (MAP) are effective, particularly for meats, but provide minimal shelf life extension for fish.

    Shelf Life Comparison

    • Shelf life (in weeks) at 0.0 - 4.0°C:
      • Lean fish:
        • Air: 1-2,
        • VP: 1-2,
        • MAP: 1-3
      • Fatty fish:
        • Air: 1-2,
        • VP: 1-2,
        • MAP: 1-3
    • Meat products show significantly longer shelf lives under similar conditions compared to fish products.

    Microbial Spoilage

    • Aerobic spoilage in meats is caused primarily by Pseudomonas spp., which are inhibited in anaerobic conditions, shifting spoilage to Gram-positive lactic acid bacteria.
    • Fish spoil primarily from Shewanella putrefaciens under aerobic conditions, countered by high CO2 levels in packaged fish.
    • Photobacterium phosphoreum, a Gram-negative organism, is identified as the primary spoilage microorganism in vacuum-packaged cod, growing well under anaerobic conditions.

    Non-Microbial Spoilage Reactions

    • Increased CO2 causes pH decrease (0.2-0.3 units), affecting muscle protein water-holding capacity, leading to higher drip loss in some fish.
    • Sensory quality of fish in high CO2 environments may be compromised, particularly at 100% CO2, while up to 60% CO2 shows minimal texture impact on cod.

    Refrigerated Seawater (RSW) Systems

    • RSW + CO2 improves the shelf life of certain fish products, compared to ice storage.
    • CO2 can prolong the shelf life of pink shrimp significantly, but may adversely affect color and texture in other species like mackerel.

    Factors Affecting Quality and Storage Life

    • Evisceration generally enhances quality and shelf life, particularly in lean species like cod, where ungutted fish show rapid quality degradation.
    • Gutting increases exposure to air, raising oxidation risks, leading to discoloration.

    Species-Specific Insights

    • Fatty fish like herring and sardines are often stored ungutted due to challenges with discoloration and rancidity.
    • Quality of perishable fish species is affected by species, fishing grounds, fishing methods, and seasonal factors.

    Intrinsic Factors of Spoilage

    • Spoilage is slower in larger fish, flat fish tend to keep better, and lean fish have longer storage capabilities than fatty species.
    • Factors such as rough handling lead to increased spoilage rates due to physical damage increasing bacterial access.

    Bacterial Growth and Spoilage Rate

    • Post-mortem pH and fat content directly influence spoilage rates; higher pH and fat content generally lead to faster spoilage.
    • Bacterial growth rates differ among species, impacting overall shelf life.

    Environmental and Temperature Influences

    • Cold-water species generally exhibit shorter iced shelf lives than tropical species, which have been reported to outperform in storage longevity.
    • Historical studies have shown some tropical fish maintain freshness in ice for 20-30 days, indicating a significant difference in spoilage dynamics between warm and cold-water species.### Fish Shelf Life Comparison
    • Fish from warm waters generally have longer shelf lives compared to those from temperate waters.
    • Freshwater fish species exhibit longer shelf lives than marine species.
    • Tropical marine fish can last 12-35 days when stored in ice, whereas temperate marine fish last 2-21 days.
    • Temperate freshwater fish shelf life ranges from 9 to 20 days.

    Factors Affecting Fish Spoilage

    • Prolonged shelf life in tropical fish may be related to lower levels of Trimethylamine (TMA) and Total Volatile Nitrogen (TVN) during storage.
    • Pseudomonas spp. are often responsible for spoilage in tropical fish, differing from Shewanella spp. which produce TMA and sulfides.
    • The absence of TMA and TVN in some tropical fish suggests spoilage mechanisms that might not involve typical bacteria.
    • Tropical fish exhibit a lag phase of 1-2 weeks before bacterial growth resumes when stored in ice.

    Bacterial Flora Influences

    • Gram-negative bacteria such as Pseudomonas and Acinetobacter are prevalent in tropical fish, potentially influencing spoilage rates.
    • Studies show high percentages (40-90%) of tropical fish bacteria can grow at chill temperatures (7°C).
    • Tropical fish tend to have slower spoilage rates compared to temperate fish, supporting the adaptation hypothesis.

    Physiological Differences

    • pH levels of tropical fish measured between 6-7, lower than some temperate species, may contribute to longer shelf life.
    • The thick skin of tropical fish might also play a role in preservation, though further research on skin properties is needed.

    Off-Flavours in Fish

    • Off-flavours in fish can arise from diet, leading to taints such as "mineral oil" from planktonic molluscs.
    • Bitter tastes in herring can be due to larvae from Mytilus spp., while muddy-earthy taints in freshwater fish stem from geosmin and 2-methylisoborneol.
    • Iodine-like flavours may indicate the presence of volatile bromophenolic compounds derived from marine organisms.
    • Environmental factors, such as oil spills, can cause oil taint due to soluble hydrocarbon compounds that accumulate in fish flesh.

    Storage and Handling Practices

    • Proper handling, such as rapid chilling of ungutted fish, is crucial for maintaining quality.
    • The type of bacterial flora and environmental conditions before and after catch impact fish longevity and quality.

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    Explore the fascinating world of fish, from their anatomy and physiology to their classification and taxonomy. This quiz covers various groups, habitats, and characteristics that define fish as aquatic vertebrates. Test your knowledge on the diversity of over 20,000 species and their evolutionary relationships.

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