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Seafood Safety. Joong-Han Shin, Barbara Rasco & Dong-Hyun Kang Department of Food Science and Human Nutrition Washington State University Tyler Greeson, ClearSprings Foods. Current Hot Issues. Mercury in fish (California Proposition 65 case) Environmental contaminants and pollution

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Seafood Safety

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Seafood Safety

Joong-Han Shin, Barbara Rasco & Dong-Hyun Kang

Department of Food Science and Human Nutrition Washington State University

Tyler Greeson, ClearSprings Foods


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Current Hot Issues

  • Mercury in fish (California Proposition 65 case)

  • Environmental contaminants and pollution

  • GM foods (they’re back…)

  • Food additives (colorants)

  • Microbial contamination


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Risks of microbial contamination in aquatic food products

  • Raw molluscan shellfish – Vibrio spp., bacterial toxins, fecal pathogens

  • Raw fish – Parasites and various

    bacteria (killed by heating)


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Risks of microbial contamination in aquatic food products

  • Ready-to-eat and smoked fish -

    • Listeria monocytogenes

    • Vibrio spp.

    • Clostridium botulinum (regulatory issue)

    • Mesophiles from humans or warm blooded animals (Salmonella spp., E. coli)


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Listeria monocytogenes

  • Gram-positive bacterium, motile by means of flagella

  • Isolated from soil, sediments, estuaries, and other environmental sources

  • Grows at temperatures as low as –0.1°C and hıgh salt (up to 10%)


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Listeriosis

  • Asymptomatic or mild flu-like symptoms

  • Immunocompromised:septicemia or

    meningoencephalitis

  • Infants: spontaneous miscarriage, stillbirth, development of meningitis within a few days of birth

  • Fatality: elderly and children if untreated


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Listeria in foods

  • The vast majority of cases are sporadic,

    making epidemiological links to food

    very difficult (CDC, 1987)


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Projected number of Listeria outbreaks

  • 2,500 cases per year. Possibly 500 deaths

  • Overall prevalence in RTE food supply is 1.8% (31,705 tested)

  • Highest levels >102/g in lunch meat and smoked fish


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Listeria in seafoods

  • The incidence of L. monocytogenes in cold-smoked or cured salmon ranges from 6 to 50%

  • FDA/USDA risk assessments estimates are that 15% of all smoked fish is contaminated with L. monocytogenes

  • 17% of vacuum-packed crawfish tails

    and 25.8% of lightly pickled fish are contamınated


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Listeria contamination patterns

  • Rate of contamınatıon of raw finfish for smoking range from 2 to 30%

  • 12% of raw shellfish and 8% of raw crab

  • 28-44% of environmental samples (floor, surfaces, drains) from smoked fish plants

  • 4.5% of meat processing plant

    refrigerators

  • 3.1% retail refrigerators


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Temperature abuse makes Listeria problem worse

  • 26% of refrigerators average >8C (France)

  • 33.3% of refrigerators > 7ºC (UK)

  • 55% of domestic and 32% of retail store refrigerators > 9ºC (Greece)

  • Refrigerators of 70% elderly consumers

    >6ºC (UK)


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Regulation of Listeria

  • zero tolerance for L. monocytogenes in cooked and ready-to-eat food by USDA-FSIS and FDA

  • Both agencies at theır dıscretıon, can hold or detain products at the food processing plant, request a voluntary recall or seize products. Numerous seafood producers have ınıtıated recalls, even ın cases where there have been no ıllnesses.


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Recent recalls of trout products

  • Food recall involves: cost of product, cost to cover, lost markets, and damage of company’s reputation.

  • Direct costs of recall are ~10% of total


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Seafood packaging

  • FDA concern with safety of vacuum packaging

  • Modified atmosphere packaging (MAP)

  • MAP alter the gaseous environment in the immediate vicinity of the product

  • Slows microbial growth and enzyme activity

  • MAP may inhibit the growth of L. monocytogenes in fish at refrigerated temperatures


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Methods

  • L. monocytogenes strains

    ATCC 19114, 7644, 19113

  • Raw and smoked rainbow trout (Oncorhynchus mykiss)

  • Enumeration on modified Oxford medium and plate count agar


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Methods

  • Packaging method

    - air-packaging

    - vacuum packaging

    - nitrogen gas flushing

    - nitrogen flushing & vacuum packaging

  • Storage at 3°C or 7°C (mild thermal abuse)

  • Sensory evaluation


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Effect of MAP on growth of L. monocytogenes in fresh trout (3°C)


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Effect of MAP on growth of L. monocytogenes in fresh trout (7°C)


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Effect of MAP on growth of endogenous microflora in fresh trout (3°C)


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Effect of MAP on growth of endogenous microflora in fresh trout (7°C)


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Aroma changes in fresh trout aroma during storage (3 & 7°C)


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Effect of MAP on growth of L. monocytogenes in smoked trout (3°C)


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Effect of MAP on growth of L. monocytogenes in smoked trout (7°C)


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Effect of MAP on growth of endogenous microflora in smoked trout (3°C)


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Effect of MAP on growth of endogenous microflora in smoked trout (7°C)


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Aroma changes in smoked trout during storage (3 & 7°C)


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Conclusions

  • 3  C: L. monocytogenes in fresh and smoked trout remained at initial levels during storage. MAP had no effect.

  • 7  C: L. monocytogenes increased up to 2 log in fresh trout, 4 log in smoked trout during storage. MAP had no effect.

  • MAP did not prevent the growth of endogenous microflora


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Conclusions

  • Fresh trout: aroma of Nitrogen & Nitrogen-Vacuum packaging remained acceptable for 20 days. Product would be spoiled before Listeria levels would become high.

  • Smoked trout:acceptable aroma for 30 days.


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Conclusions

  • Smoked trout with moderately high initial levels of Listeria (log 2) could be unsafe in 10-15 days at mild thermal abuse (7oC) and not appear to be spoiled.


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