Podcast
Questions and Answers
What is primarily responsible for spoilage of fresh fish products during chill storage?
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?
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?
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?
What effect do psychrotrophic organisms have on fish spoilage at low temperatures?
What common practice is used in industrialized countries to extend the shelf life of fresh fish?
What common practice is used in industrialized countries to extend the shelf life of fresh fish?
Which bacterium's growth rate is significantly affected by temperature in the context of fish spoilage?
Which bacterium's growth rate is significantly affected by temperature in the context of fish spoilage?
Which statement best describes the relationship between temperature and the shelf life of seafood?
Which statement best describes the relationship between temperature and the shelf life of seafood?
What is the result of storing seafood products at higher temperatures?
What is the result of storing seafood products at higher temperatures?
What compound is primarily responsible for the 'mineral oil' or 'petrol' off-flavour in fish?
What compound is primarily responsible for the 'mineral oil' or 'petrol' off-flavour in fish?
Which species' larvae are known to cause a bitter taste in herring?
Which species' larvae are known to cause a bitter taste in herring?
What are the main compounds responsible for the muddy-earthy taint in freshwater fish?
What are the main compounds responsible for the muddy-earthy taint in freshwater fish?
What type of off-flavour is associated with fish and shrimp from the marine environment due to certain compounds?
What type of off-flavour is associated with fish and shrimp from the marine environment due to certain compounds?
What causes oil taint in fish flesh in certain areas?
What causes oil taint in fish flesh in certain areas?
What factor is primarily used to express the relationship between temperature and relative rate of spoilage (RRS)?
What factor is primarily used to express the relationship between temperature and relative rate of spoilage (RRS)?
Which equation has shown limitations when analyzing the effect of a wide range of temperatures on spoilage?
Which equation has shown limitations when analyzing the effect of a wide range of temperatures on spoilage?
What is the significance of the parameter Tmin in the square root model?
What is the significance of the parameter Tmin in the square root model?
What type of bacteria is associated with relatively low storage temperatures (0-5°C)?
What type of bacteria is associated with relatively low storage temperatures (0-5°C)?
How does the spoilage microflora change with different storage temperatures?
How does the spoilage microflora change with different storage temperatures?
What is the relationship of RRS for tropical fish stored at 20°-30°C compared to fish stored at 0°C?
What is the relationship of RRS for tropical fish stored at 20°-30°C compared to fish stored at 0°C?
Which spoilage model has recently been developed for tropical fish?
Which spoilage model has recently been developed for tropical fish?
What is the role of an electronic time/temperature function integrator in shelf life prediction?
What is the role of an electronic time/temperature function integrator in shelf life prediction?
Which factor does not influence the temperature models based on the relative rate concept?
Which factor does not influence the temperature models based on the relative rate concept?
Which spoilage prediction method has recently become more accessible due to cost reductions?
Which spoilage prediction method has recently become more accessible due to cost reductions?
According to the square root model, how are microbial growth rates plotted against temperature?
According to the square root model, how are microbial growth rates plotted against temperature?
Which temperature is considered a threshold for growth of psychrotrophic bacteria?
Which temperature is considered a threshold for growth of psychrotrophic bacteria?
What determines the shelf life of fish at given storage temperatures?
What determines the shelf life of fish at given storage temperatures?
What significant factor affects the quality of fatty fish during storage?
What significant factor affects the quality of fatty fish during storage?
What is the main benefit of superchilling fish products?
What is the main benefit of superchilling fish products?
What temperature range defines superchilling?
What temperature range defines superchilling?
What negative effect can superchilling have on some fish species?
What negative effect can superchilling have on some fish species?
What does the term 'demerit point system' refer to?
What does the term 'demerit point system' refer to?
What technology has been developed to help utilize superchilling at sea?
What technology has been developed to help utilize superchilling at sea?
How might RSW (refrigerated sea water) systems affect fish species?
How might RSW (refrigerated sea water) systems affect fish species?
What was observed regarding the impact of delayed chilling on white-fleshed lean fish?
What was observed regarding the impact of delayed chilling on white-fleshed lean fish?
At which temperatures was the daily rate of change in DT values accurately predicted?
At which temperatures was the daily rate of change in DT values accurately predicted?
What is a critical factor in the effectiveness of chilling for fish quality?
What is a critical factor in the effectiveness of chilling for fish quality?
What is the outcome of lipids oxidation in fatty fish?
What is the outcome of lipids oxidation in fatty fish?
Which shelf life prediction model is mentioned for superchilled products?
Which shelf life prediction model is mentioned for superchilled products?
What could happen to cod stored at lower temperatures for extended periods?
What could happen to cod stored at lower temperatures for extended periods?
What is the primary benefit of superchilling shrimp from Pakistan compared to traditional ice storage?
What is the primary benefit of superchilling shrimp from Pakistan compared to traditional ice storage?
At what temperature does the percentage of frozen water in superchilled fish reach 70%?
At what temperature does the percentage of frozen water in superchilled fish reach 70%?
Which fish species' shelf life is improved by superchilling at -3°C compared to storage at 0°C?
Which fish species' shelf life is improved by superchilling at -3°C compared to storage at 0°C?
What caused the negative effects on sensory quality in some fish species when using superchilling?
What caused the negative effects on sensory quality in some fish species when using superchilling?
What was the impact of hygienic handling compared to storage conditions on the shelf life of fish in the experiments?
What was the impact of hygienic handling compared to storage conditions on the shelf life of fish in the experiments?
What is the suggested reason for using clean fish boxes rather than strict hygienic measures?
What is the suggested reason for using clean fish boxes rather than strict hygienic measures?
What substance is suggested for use as part of modified atmosphere packaging to prolong the storage life of fish?
What substance is suggested for use as part of modified atmosphere packaging to prolong the storage life of fish?
What is a significant concern regarding the use of radioactive irradiation in fish storage?
What is a significant concern regarding the use of radioactive irradiation in fish storage?
What was the conclusion regarding the drainage of melt-water in fish boxes?
What was the conclusion regarding the drainage of melt-water in fish boxes?
Which method for decontaminating fish is less favored due to the off-flavors it creates?
Which method for decontaminating fish is less favored due to the off-flavors it creates?
What storage condition was superior for cultured fish species in terms of reducing spoilage?
What storage condition was superior for cultured fish species in terms of reducing spoilage?
What does a K-value of 20% indicate in fish freshness assessment?
What does a K-value of 20% indicate in fish freshness assessment?
Which is NOT a method used to extend fish storage life according to the content?
Which is NOT a method used to extend fish storage life according to the content?
How does initial bacterial contamination affect the organoleptic quality of stored fish?
How does initial bacterial contamination affect the organoleptic quality of stored fish?
How do high CO2 concentrations affect microbial growth in food products?
How do high CO2 concentrations affect microbial growth in food products?
What primary organisms cause spoilage in meat under aerobic conditions?
What primary organisms cause spoilage in meat under aerobic conditions?
What is the typical effect of vacuum packaging (VP) on the shelf life of fish products compared to meat?
What is the typical effect of vacuum packaging (VP) on the shelf life of fish products compared to meat?
Which organism is primarily responsible for spoilage in packed cod?
Which organism is primarily responsible for spoilage in packed cod?
Why does the spoilage pattern of packed cod differ from that of other fish products?
Why does the spoilage pattern of packed cod differ from that of other fish products?
What effect does packaging fish in high CO2 concentrations have on bacteria like Shewanella putrefaciens?
What effect does packaging fish in high CO2 concentrations have on bacteria like Shewanella putrefaciens?
What is one consequence of decreased pH in fish stored in high CO2 concentrations?
What is one consequence of decreased pH in fish stored in high CO2 concentrations?
What characteristic of spoiled VP and MAP cod is highlighted in the content?
What characteristic of spoiled VP and MAP cod is highlighted in the content?
How does the shelf life of fish in modified atmosphere packaging (MAP) compare to that of meat products?
How does the shelf life of fish in modified atmosphere packaging (MAP) compare to that of meat products?
What is one effect of high CO2 concentrations on the texture of cod?
What is one effect of high CO2 concentrations on the texture of cod?
Which of the following statements is true about CO2's effect on Photobacterium phosphoreum?
Which of the following statements is true about CO2's effect on Photobacterium phosphoreum?
What happens to the color of fish stored in high CO2 concentrations?
What happens to the color of fish stored in high CO2 concentrations?
What is associated with the growth of Photobacterium phosphoreum in anaerobic conditions?
What is associated with the growth of Photobacterium phosphoreum in anaerobic conditions?
In what kind of fish packaging does non-microbial spoilage mainly contribute to spoilage patterns?
In what kind of fish packaging does non-microbial spoilage mainly contribute to spoilage patterns?
What is the primary reason that bacteria are often thought to not be involved in the spoilage of tropical fish?
What is the primary reason that bacteria are often thought to not be involved in the spoilage of tropical fish?
Which bacterial species are primarily responsible for the spoilage of iced tropical fish?
Which bacterial species are primarily responsible for the spoilage of iced tropical fish?
What characteristic odour is associated with the spoilage caused by Shewanella spp. in tropical fish?
What characteristic odour is associated with the spoilage caused by Shewanella spp. in tropical fish?
What pH value range has been reported for tropical fish species?
What pH value range has been reported for tropical fish species?
What is a major factor that affects the shelf life of fresh fish compared to other meats, like chilled beef?
What is a major factor that affects the shelf life of fresh fish compared to other meats, like chilled beef?
What factor may contribute to the longer shelf life of tropical fish compared to temperate fish?
What factor may contribute to the longer shelf life of tropical fish compared to temperate fish?
What observation about bacterial growth in tropical fish storage distinguishes it from temperate fish?
What observation about bacterial growth in tropical fish storage distinguishes it from temperate fish?
Which factor is not cited as a reason for the longer iced storage life of tropical fish?
Which factor is not cited as a reason for the longer iced storage life of tropical fish?
How do the bacterial counts generally observed on tropical fish compare to those on temperate fish after capture?
How do the bacterial counts generally observed on tropical fish compare to those on temperate fish after capture?
What temperature range has been found conducive for the growth of bacteria on Nile perch?
What temperature range has been found conducive for the growth of bacteria on Nile perch?
What issue has affected the accuracy of bacterial counts in some studies of tropical fish?
What issue has affected the accuracy of bacterial counts in some studies of tropical fish?
Which conclusion can be drawn about tropical fish spoilage compared to temperate fish spoilage?
Which conclusion can be drawn about tropical fish spoilage compared to temperate fish spoilage?
Why might lower numbers of psychrotrophic bacteria not explain the extended shelf life of tropical fish?
Why might lower numbers of psychrotrophic bacteria not explain the extended shelf life of tropical fish?
What characteristic of the bacterial flora in Narragansett Bay was observed over a two-year survey?
What characteristic of the bacterial flora in Narragansett Bay was observed over a two-year survey?
Which type of fish is generally accepted as having a longer shelf life when stored in ice?
Which type of fish is generally accepted as having a longer shelf life when stored in ice?
What is a significant factor contributing to the longer shelf life of larger fish?
What is a significant factor contributing to the longer shelf life of larger fish?
Which species showed no difference in spoilage rates between gutted and ungutted individuals?
Which species showed no difference in spoilage rates between gutted and ungutted individuals?
What is the primary reason that rough handling of fish leads to faster spoilage?
What is the primary reason that rough handling of fish leads to faster spoilage?
Which of the following fish tends to spoil faster due to its higher fat content?
Which of the following fish tends to spoil faster due to its higher fat content?
How does the spoilage rate of tropical fish compare to that of temperate freshwater fish?
How does the spoilage rate of tropical fish compare to that of temperate freshwater fish?
What role does pH play in determining the shelf life of fish?
What role does pH play in determining the shelf life of fish?
Which intrinsic factor is NOT mentioned as affecting spoilage rate in fish?
Which intrinsic factor is NOT mentioned as affecting spoilage rate in fish?
What does TMAO content typically affect in fish?
What does TMAO content typically affect in fish?
Which characteristic of flatfish contributes to their better preservation compared to round fish?
Which characteristic of flatfish contributes to their better preservation compared to round fish?
Under what condition do fatty fish spoil mainly due to oxidation?
Under what condition do fatty fish spoil mainly due to oxidation?
Which factor is confirmed to slow spoilage in fish?
Which factor is confirmed to slow spoilage in fish?
What is a conclusion regarding the spoilage rates among different fish species?
What is a conclusion regarding the spoilage rates among different fish species?
What was noted as a significant negative effect of adding CO2 to RSW systems?
What was noted as a significant negative effect of adding CO2 to RSW systems?
How does CO2 affect the shelf life of pink shrimps compared to ice storage?
How does CO2 affect the shelf life of pink shrimps compared to ice storage?
What factor must be considered when evaluating the cost of RSW + CO2 systems?
What factor must be considered when evaluating the cost of RSW + CO2 systems?
What is the primary reason why MAP has little practical application with fish products when compared to meat products?
What is the primary reason why MAP has little practical application with fish products when compared to meat products?
What immediate effect does gutting fish have post-catch?
What immediate effect does gutting fish have post-catch?
What phenomenon occurs more frequently in ungutted fish during heavy feeding periods?
What phenomenon occurs more frequently in ungutted fish during heavy feeding periods?
Why is gutting lean species like cod compulsory in many North European countries?
Why is gutting lean species like cod compulsory in many North European countries?
What is the primary consequence of not gutting cod after catch?
What is the primary consequence of not gutting cod after catch?
What is a noted challenge when processing small- and medium-sized fatty fish?
What is a noted challenge when processing small- and medium-sized fatty fish?
What is an effect of high CO2 concentrations on fish quality?
What is an effect of high CO2 concentrations on fish quality?
During what condition is autolysis likely to intensify in fish?
During what condition is autolysis likely to intensify in fish?
What is one of the main reasons for the negative effects of CO2 on whole fish?
What is one of the main reasons for the negative effects of CO2 on whole fish?
Why is the chemical makeup of gutted and ungutted fish not useful for differentiation?
Why is the chemical makeup of gutted and ungutted fish not useful for differentiation?
What does the RSW system do to enhance fish preservation?
What does the RSW system do to enhance fish preservation?
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.
