Quality Changes in Chilled Fish

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Questions and Answers

What is primarily responsible for spoilage of fresh fish products during chill storage?

Microbiological activity (correct)

Physical damage

Enzymatic activity

Chemical reactions

At what temperature does microbial activity in fish spoilage notably decrease?

Below 10°C (correct)

Below 5°C

At 0°C

At 15°C

How does storage temperature affect the relative rate of spoilage (RRS) of seafood products?

Higher temperatures increase RRS (correct)

Lower temperatures increase RRS

Higher temperatures reduce RRS

RRS is unaffected by temperature changes

What effect do psychrotrophic organisms have on fish spoilage at low temperatures?

They have extended lag phases Signup and view all the answers

What common practice is used in industrialized countries to extend the shelf life of fresh fish?

Storing in ice at 0°C Signup and view all the answers

Which bacterium's growth rate is significantly affected by temperature in the context of fish spoilage?

Shewanella putrefaciens Signup and view all the answers

Which statement best describes the relationship between temperature and the shelf life of seafood?

Shelf life decreases with rising temperatures Signup and view all the answers

What is the result of storing seafood products at higher temperatures?

Increased microbial growth Signup and view all the answers

What compound is primarily responsible for the 'mineral oil' or 'petrol' off-flavour in fish?

Dimethyl-B-propiothetin Signup and view all the answers

Which species' larvae are known to cause a bitter taste in herring?

Mytilus spp. Signup and view all the answers

What are the main compounds responsible for the muddy-earthy taint in freshwater fish?

Geosmin and 2-methylisoborneol Signup and view all the answers

What type of off-flavour is associated with fish and shrimp from the marine environment due to certain compounds?

Iodine-like Signup and view all the answers

What causes oil taint in fish flesh in certain areas?

Accumulation of hydrocarbons from crude oil Signup and view all the answers

What factor is primarily used to express the relationship between temperature and relative rate of spoilage (RRS)?

S-shaped spoilage curve Signup and view all the answers

Which equation has shown limitations when analyzing the effect of a wide range of temperatures on spoilage?

Arrhenius Equation Signup and view all the answers

What is the significance of the parameter Tmin in the square root model?

It expresses the theoretical minimum temperature of growth. Signup and view all the answers

What type of bacteria is associated with relatively low storage temperatures (0-5°C)?

Pseudomonas spp. Signup and view all the answers

How does the spoilage microflora change with different storage temperatures?

Different bacterial species are responsible at varying temperatures. Signup and view all the answers

What is the relationship of RRS for tropical fish stored at 20°-30°C compared to fish stored at 0°C?

Approximately 25 times higher. Signup and view all the answers

Which spoilage model has recently been developed for tropical fish?

Tropical spoilage model Signup and view all the answers

What is the role of an electronic time/temperature function integrator in shelf life prediction?

It predicts RRS based on temperature history. Signup and view all the answers

Which factor does not influence the temperature models based on the relative rate concept?

Initial product quality Signup and view all the answers

Which spoilage prediction method has recently become more accessible due to cost reductions?

Time/temperature loggers and computer models Signup and view all the answers

According to the square root model, how are microbial growth rates plotted against temperature?

As a straight line. Signup and view all the answers

Which temperature is considered a threshold for growth of psychrotrophic bacteria?

263 Kelvin (-10°C) Signup and view all the answers

What determines the shelf life of fish at given storage temperatures?

The temperature spoilage model Signup and view all the answers

What significant factor affects the quality of fatty fish during storage?

Exposure to sunlight and wind before chilling Signup and view all the answers

What is the main benefit of superchilling fish products?

It enables longer shelf life Signup and view all the answers

What temperature range defines superchilling?

0°C to -4°C Signup and view all the answers

What negative effect can superchilling have on some fish species?

Inferior appearance and texture Signup and view all the answers

What does the term 'demerit point system' refer to?

A system for measuring quality scores over time Signup and view all the answers

What technology has been developed to help utilize superchilling at sea?

Frigido-system Signup and view all the answers

How might RSW (refrigerated sea water) systems affect fish species?

Impart a salty taste due to seawater absorption Signup and view all the answers

What was observed regarding the impact of delayed chilling on white-fleshed lean fish?

It can cause muscle tissue to rupture. Signup and view all the answers

At which temperatures was the daily rate of change in DT values accurately predicted?

0°C to 10°C Signup and view all the answers

What is a critical factor in the effectiveness of chilling for fish quality?

The speed of chilling after capture Signup and view all the answers

What is the outcome of lipids oxidation in fatty fish?

Rancid off-flavors Signup and view all the answers

Which shelf life prediction model is mentioned for superchilled products?

Square root spoilage model Signup and view all the answers

What could happen to cod stored at lower temperatures for extended periods?

May be unsuitable for filleting Signup and view all the answers

What is the primary benefit of superchilling shrimp from Pakistan compared to traditional ice storage?

Improved shelf life Signup and view all the answers

At what temperature does the percentage of frozen water in superchilled fish reach 70%?

-3°C Signup and view all the answers

Which fish species' shelf life is improved by superchilling at -3°C compared to storage at 0°C?

Mackerel Signup and view all the answers

What caused the negative effects on sensory quality in some fish species when using superchilling?

Formation of large ice crystals Signup and view all the answers

What was the impact of hygienic handling compared to storage conditions on the shelf life of fish in the experiments?

Hygiene had no impact whatsoever Signup and view all the answers

What is the suggested reason for using clean fish boxes rather than strict hygienic measures?

Ineffectiveness of strict measures Signup and view all the answers

What substance is suggested for use as part of modified atmosphere packaging to prolong the storage life of fish?

Carbon Dioxide Signup and view all the answers

What is a significant concern regarding the use of radioactive irradiation in fish storage?

Public health and acceptability Signup and view all the answers

What was the conclusion regarding the drainage of melt-water in fish boxes?

It has no significant impact Signup and view all the answers

Which method for decontaminating fish is less favored due to the off-flavors it creates?

Chlorinated water washing Signup and view all the answers

What storage condition was superior for cultured fish species in terms of reducing spoilage?

Superchilling at -3°C Signup and view all the answers

What does a K-value of 20% indicate in fish freshness assessment?

Moderate freshness Signup and view all the answers

Which is NOT a method used to extend fish storage life according to the content?

High-temperature storage Signup and view all the answers

How does initial bacterial contamination affect the organoleptic quality of stored fish?

Only noticeable after two weeks Signup and view all the answers

How do high CO2 concentrations affect microbial growth in food products?

They reduce microbial growth. Signup and view all the answers

What primary organisms cause spoilage in meat under aerobic conditions?

Pseudomonas spp. Signup and view all the answers

What is the typical effect of vacuum packaging (VP) on the shelf life of fish products compared to meat?

Fish shelf life is not affected. Signup and view all the answers

Which organism is primarily responsible for spoilage in packed cod?

Photobacterium phosphoreum Signup and view all the answers

Why does the spoilage pattern of packed cod differ from that of other fish products?

It is dominated by Gram-negative organisms. Signup and view all the answers

What effect does packaging fish in high CO2 concentrations have on bacteria like Shewanella putrefaciens?

Strongly inhibits their growth. Signup and view all the answers

What is one consequence of decreased pH in fish stored in high CO2 concentrations?

Increased drip loss. Signup and view all the answers

What characteristic of spoiled VP and MAP cod is highlighted in the content?

High levels of TMA. Signup and view all the answers

How does the shelf life of fish in modified atmosphere packaging (MAP) compare to that of meat products?

It is shorter. Signup and view all the answers

What is one effect of high CO2 concentrations on the texture of cod?

Texture is reduced at 100% CO2. Signup and view all the answers

Which of the following statements is true about CO2's effect on Photobacterium phosphoreum?

It has a limited effect on its growth. Signup and view all the answers

What happens to the color of fish stored in high CO2 concentrations?

The belly flaps and cornea may change color. Signup and view all the answers

What is associated with the growth of Photobacterium phosphoreum in anaerobic conditions?

Increased growth rate. Signup and view all the answers

In what kind of fish packaging does non-microbial spoilage mainly contribute to spoilage patterns?

High CO2 MAP fish. Signup and view all the answers

What is the primary reason that bacteria are often thought to not be involved in the spoilage of tropical fish?

The spoilage of tropical fish is not associated with TMA and TVN development. Signup and view all the answers

Which bacterial species are primarily responsible for the spoilage of iced tropical fish?

Pseudomonas spp. and Shewanella putrefaciens Signup and view all the answers

What characteristic odour is associated with the spoilage caused by Shewanella spp. in tropical fish?

Putrid, sulphide odours Signup and view all the answers

What pH value range has been reported for tropical fish species?

6-7 Signup and view all the answers

What is a major factor that affects the shelf life of fresh fish compared to other meats, like chilled beef?

Postmortem pH levels Signup and view all the answers

What factor may contribute to the longer shelf life of tropical fish compared to temperate fish?

Thicker skin properties Signup and view all the answers

What observation about bacterial growth in tropical fish storage distinguishes it from temperate fish?

Tropical fish have a longer lag phase before bacterial growth begins. Signup and view all the answers

Which factor is not cited as a reason for the longer iced storage life of tropical fish?

Higher oxygen levels in tropical waters Signup and view all the answers

How do the bacterial counts generally observed on tropical fish compare to those on temperate fish after capture?

Tropical fish maintain lower overall bacterial counts. Signup and view all the answers

What temperature range has been found conducive for the growth of bacteria on Nile perch?

7°C Signup and view all the answers

What issue has affected the accuracy of bacterial counts in some studies of tropical fish?

Use of selective media and incubation at high temperatures. Signup and view all the answers

Which conclusion can be drawn about tropical fish spoilage compared to temperate fish spoilage?

Spoilage rates differ primarily due to bacterial growth rates. Signup and view all the answers

Why might lower numbers of psychrotrophic bacteria not explain the extended shelf life of tropical fish?

Research indicates little difference in numbers and shelf life. Signup and view all the answers

What characteristic of the bacterial flora in Narragansett Bay was observed over a two-year survey?

No changes in the composition were noted despite temperature fluctuations. Signup and view all the answers

Which type of fish is generally accepted as having a longer shelf life when stored in ice?

Lean fish Signup and view all the answers

What is a significant factor contributing to the longer shelf life of larger fish?

Lower surface/volume ratio Signup and view all the answers

Which species showed no difference in spoilage rates between gutted and ungutted individuals?

South American hake Signup and view all the answers

What is the primary reason that rough handling of fish leads to faster spoilage?

Physical damage allowing bacterial access Signup and view all the answers

Which of the following fish tends to spoil faster due to its higher fat content?

Mackerel Signup and view all the answers

How does the spoilage rate of tropical fish compare to that of temperate freshwater fish?

Tropical fish often have prolonged shelf lives Signup and view all the answers

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

Fish species have highly variable post mortem pH Signup and view all the answers

Which intrinsic factor is NOT mentioned as affecting spoilage rate in fish?

Color of the fish Signup and view all the answers

What does TMAO content typically affect in fish?

Chemical spoilage profile Signup and view all the answers

Which characteristic of flatfish contributes to their better preservation compared to round fish?

Presence of bacteriolytic enzymes in slime Signup and view all the answers

Under what condition do fatty fish spoil mainly due to oxidation?

Under aerobic storage Signup and view all the answers

Which factor is confirmed to slow spoilage in fish?

Lower storage temperature Signup and view all the answers

What is a conclusion regarding the spoilage rates among different fish species?

Different spoilage rates can be attributed to bacterial growth influences Signup and view all the answers

What was noted as a significant negative effect of adding CO2 to RSW systems?

Color and texture degradation of fish Signup and view all the answers

How does CO2 affect the shelf life of pink shrimps compared to ice storage?

Shelf life can be more than doubled Signup and view all the answers

What factor must be considered when evaluating the cost of RSW + CO2 systems?

Cost of inert materials for heat exchange Signup and view all the answers

What is the primary reason why MAP has little practical application with fish products when compared to meat products?

Convenience of packaging for handling Signup and view all the answers

What immediate effect does gutting fish have post-catch?

Increases risk of discoloration and oxidation Signup and view all the answers

What phenomenon occurs more frequently in ungutted fish during heavy feeding periods?

Belly-burst Signup and view all the answers

Why is gutting lean species like cod compulsory in many North European countries?

To prevent spoilage and off-odors Signup and view all the answers

What is the primary consequence of not gutting cod after catch?

Visible discoloration and off-odors Signup and view all the answers

What is a noted challenge when processing small- and medium-sized fatty fish?

Discoloration and rancidity issues Signup and view all the answers

What is an effect of high CO2 concentrations on fish quality?

May negatively affect color and texture Signup and view all the answers

During what condition is autolysis likely to intensify in fish?

When fish are well-fed before catch Signup and view all the answers

What is one of the main reasons for the negative effects of CO2 on whole fish?

Discoloration and texture issues Signup and view all the answers

Why is the chemical makeup of gutted and ungutted fish not useful for differentiation?

Volatile compounds are mostly in the gut area Signup and view all the answers

What does the RSW system do to enhance fish preservation?

Regulate the temperature and pH of storage Signup and view all the answers

Study Notes

The Effect of Storage Temperature

Chill storage typically occurs within a temperature range of 0-25°C, significantly affecting both enzymatic and microbiological activity.
Microbiological activity is more crucial than enzymatic activity in the temperature range of 0-10°C; many bacteria struggle to grow at temperatures below 10°C.
Storage at low temperatures (e.g., 0°C in ice) markedly extends the shelf life of fresh fish products due to slower microbial spoilage.
Relative rates of spoilage (RRS) provide a formulaic approach to estimate the shelf life of various seafood products at different temperatures.
Australian researchers have established an S-shaped spoilage curve relationship between temperature and RRS, confirming earlier findings regarding cod spoilage.
Models like the Arrhenius Equation are found inadequate for a wide temperature range; alternative models, such as the square root spoilage model, are proposed for better predictions of microbial growth at sub-optimal temperatures.
RRS for tropical fish is found to be approximately 25 times higher than for fish stored at 0°C, necessitating new spoilage models specifically for tropical fish species.
Shelf life predictions depend on both the initial quality of the product and storage temperature, with established equations to relate these factors.
Reliable indicators of product temperature history and microbial growth can be monitored using electronic temperature loggers, facilitating better predictions for shelf life and microbial safety.

The Effect of Hygiene During Handling

Hygienic handling practices onboard fishing vessels significantly influence fish quality and storage life, starting from the moment of catching.
Experiments show that aseptic handling leads to lower bacterial contamination compared to conventional practices, yet organoleptic quality differences are not immediately evident.
Effective chilling of fish is prioritized over extreme hygienic measures, impacting storage life more significantly than initial bacterial contamination levels.
The design of fish boxes is crucial for effective chilling; boxes that allow melt-water drainage improve overall chilling efficiency without significantly contributing to cross-contamination.
Disinfection methods such as radioactive irradiation are effective but costly; concerns over food safety have led to the rejection of antibiotic treatments incorporated into ice.
Treatment with carbon dioxide (CO2) is emerging as a successful method for prolonging fish storage life, applied in chilled seawater or modified atmosphere during transportation.
Washing with chlorinated water has been attempted as a decontamination method but poses risks of off-flavors in fish; using clean seawater is recommended for rinsing freshly caught fish.### Washing Purpose and Effectiveness
Washing primarily removes visible blood and dirt from fish.
It does not significantly reduce bacteria levels or extend storage life.

Anaerobic Conditions and Carbon Dioxide

High CO2 concentrations can inhibit microbial growth, prolonging food shelf life.
Vacuum packaging (VP) and modified atmosphere packaging (MAP) extend shelf life of meat significantly but have limited effects on fish.

Microbial Spoilage in Fish and Meat

In aerobic conditions, meat spoilage is mainly caused by Gram-negative bacteria, especially Pseudomonas spp., which are inhibited in anaerobic conditions.
Fish spoilage under aerobic conditions is predominantly due to Shewanella putrefaciens.
Photobacterium phosphoreum is a significant spoilage organism for packed cod, thriving in anaerobic environments despite its resistance to CO2.

Shelf Life Influences

Shelf life of fish products varies based on species and spoilage microflora.
Fish from warm waters tend to have better MAP shelf life compared to other fish species.
Non-microbial reactions can contribute to spoilage, observed at low bacterial levels.

Drip Loss and Non-Microbial Spoilage

CO2 causes a decrease in pH, affecting water-holding capacity of muscle proteins, leading to increased drip loss in some fish species.
High CO2 concentrations (up to 60%) do not negatively affect cod texture but may alter color.
RSW (Refrigerated Seawater) may exhibit color and texture changes when combined with CO2.

Effects of Gutting on Fish Quality

Gutting is essential for preventing off-flavors and quality loss in fish, especially lean species like cod.
Quality is maintained better in gutted fish because gut bacteria and enzymes are minimized.

Variations Among Fish Species

Smaller and medium-sized fatty fish are less likely to be eviscerated immediately due to risks of discoloration and rancidity.
Lean fish generally experience a notable quality loss when ungutted, as seen with cod, which shows discoloration and off-putting odors after a few days.

Shelf Life Factors

Larger fish spoil more slowly than smaller ones; flatfish usually have better preservation than round fish.
Environmental factors like water temperature deeply affect spoilage rates; tropical fish often have prolonged shelf lives compared to temperate fish.

Conclusion on CO2 and Preservation Techniques

High CO2 concentrations can inhibit spoilage bacteria but can negatively impact fish quality.
MAP applications for seafood have limitations compared to meat.
Future applications could involve techniques aimed specifically at CO2-resistant spoilage bacteria for seafood preservation.### Factors Affecting Fish Shelf Life
High postmortem pH contributes to the shorter shelf life of fresh fish compared to chill-stored beef.
Tropical fish species, such as halibut, are believed to reach lower pH levels, potentially accounting for their longer shelf life.
Studies show most tropical fish exhibit pH values between 6-7, challenging the assumption that lower pH is a primary factor for shelf life.
Skin properties of flatfish are thought to enhance shelf life, with thicker skin common in tropical fish but lacking systematic investigation.
Fish spoilage primarily results from bacterial action, leading to hypotheses focusing on differences in bacterial flora impacting tropical fish shelf lives.

Bacterial Flora and Shelf Life

Shewan noted lower numbers of psychrotrophs on tropical fish as a reason for longer iced shelf lives; however, limited studies addressed this in 1977.
Recent studies identify Gram-negative rod-shaped bacteria (e.g., Pseudomonas, Moraxella, Acinetobacter) dominating tropical fish caught in warm waters.
Bacteria on Nile perch showed 40-90% capability to grow at 7°C, with psychrotrophic bacteria not low enough to solely explain tropical fish’s extended shelf life.
A significant lag phase of 1-2 weeks occurs for bacteria on tropical fish stored in ice, unlike temperate species which resume growth immediately post-catch.
Growth of psychrotrophic bacteria on iced tropical fish is also slower than on temperate species.
Studies indicate that bacterial adaptation plays a role, with pre-cultured bacteria growing differently based on temperature conditions prior to chilling.

Off-Flavours in Fish

Off-flavours in fish can stem from their feeding habits and certain local environmental factors, with implications for quality and consumer perception.
The planktonic mollusc, Spiratella helicina, produces a "mineral oil" flavour in fish due to dimethyl-B-propiothetin conversion to dimethylsulfide.
Bitter flavours in herring can be caused by larvae of Mytilus spp.
Freshwater fish may exhibit a muddy-earthy taint linked to geosmin and 2-methylisoborneol, compounds produced by specific bacterial taxa.
An iodine-like flavour found in some marine fish and shrimp is attributed to volatile bromophenolic compounds from marine sources.
Oil pollution can result in tainted fish flesh, with soluble hydrocarbons from crude oil being strong flavourants.

Recommendations for Fish Quality

Rapid chilling of whole, ungutted fish is crucial for maintaining quality and shelf life, as evidenced by the efforts of fishermen on South American hake trawlers.

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Description

This quiz explores the factors affecting the quality changes and shelf life of chilled fish, including storage temperature, handling hygiene, and environmental conditions. Discover how these elements interact and influence the freshness of fish products.