1Microbiology of Primary Food CommoditiesIII SeafoodsSources of microorganisms •Water•Mud• Harvesting equipment and utensils– Nets, boxes etc.•Boat surfaces– Counts have been determined to be as high as 108-109Post harvest handling of fish• Gutting and bleeding (deheading in shrimp)• Washing with sea water•Icing2From Jay, 19983Finfish• Internal flesh of healthy, live fish is sterile• Natural microbiota resides in:– Gills– Intestines (feeding fish)•Bacterial numbers:–Skin 102–106/cm2– Gills 103–105/g– Intestine• Non-feeding <102/g• Feeding 107/gMicrobial loads• Bacterial counts are affected by the method of harvesting– Counts on trawled fish 10 – 100 times greater than line-caught fish• Stirring mud during dragging out of the ocean• Compaction of the fish on the deck4Spoilage of fish• High protein content– 70%–Non-protein N:• Free aminoacids• Volatile bases such as NH3or N(CH2)3• Highly labile to direct putrefaction• Seawater fish contains more free aminoacids– Spoils faster than freshwater fishSpoilage of fish• Great autolytic spoilage–Reduced by gutting• Spoilage organisms first utilize simpler compounds such as free aminoacids– Release of volatile compounds such as NH3, taurine, creatine, anserine, TMA oxide and related compoundsSpoilage of fish• Microorganisms associated with fish spoilage– Gram-negative, oxidase positive aerobic bacteria–Pseudomonas-Shewanella, Moraxella-Acinetobacter–Pseudomonasand Shewanellaproduce TMAO and H2S• Off-odors5Spoilage of fish• Measuring volatile N compounds helps determine the freshness of fish• Desired values for shrimp and fish:– Total volatile nitrogen (TVN) <30 mg/100g• Offness of shrimp associated with >30 mg TVN/100g – Trimethylamine nitrogen (TMAN) <5 mg/100g– Total volatile bases (TVB) < 45 mg/100g• ≥ 45 mg TVB/100g associated with fish of marginal qualityShellfishShellfish•CrustaceansShrimp Crab Lobster CrayfishShellfishShellfish (cont.)•MollusksOysters Clams Scallops Squid6Spoilage of shellfish• Shellfish contain carbohydrates in their muscle– Mostly glycogen• Organisms associated with spoilage–PMA–Serratia, Pseudomonas, Proteus, Clostridium, Bacillus, Escherichia, Enterobacter, Shewanella, Lactobacillus, Flavobacterium, Micrococuus• Spoilage usually fermentativepH scale for shellfishScorepHSour or putrid5.2 or belowMusty5.7 – 5.5“off”5.8Good6.2 – 5.9Indicators of quality• Finfish and some crustaceans–TVN, TMA or TVB–pH–APC• Moluscan shellfish– Indicators of growing water quality•Fecal coliforms– Quality and safety of the food product• Fecal coliforms correlate with the presence of Salmonella7Food safety aspects• Marine vibrios–Vibrio parahaemolyticus–Vibrio vulnificus• Fecal pathogens–Salmonella–Campylobacter–Vibrio cholerae• Other pathogens–Staphylococcus aureus–Clostridium botulinumType EBacterial pathogensy = -0.0271x + 3.3399R2 = 0.9513y = 0.0002x2 - 0.0467x + 2.8253R2 = 0.9461012340 24487296Hours of storageLog10 MPN/gInabaOgawaSurvival of V. cholerae in ceviche stored at 7-8°Cy = -0.0052x2 + 0.0196x + 3.553R2 = 0.9865y = 0.015x2 - 0.4736x + 4.1985R2 = 0.91880123450 3 6 9 12 15 18 21 24Hours of storageLog10 MPN/gInabaOgawaSurvival of V. cholerae in ceviche stored at 20°C80246810012345Minutes of treatmentLog10 CFU/g020406080100Temperature (°C)V. cholerae APC Coliforms Temperature (°C)Lower Detection LimitReduction of V. cholerae, APC and coliforms in ceviche after heat pre treatment of raw ingredientsFood safety aspects•Protozoa– Myxosporidia such as Henneguya salminicola– Affects the quality of fish so eating is unlikely•Cestods–Diphyllobothrium latum• Nematodes–Anisakis simplex–Pseudoterranova decipiens–Philometraspp. from handling infested fishParasitesFood safety aspects• Hepatitis A•Norwalk• Snow mountain agent• Calicivirus• Astrovirus•NANB hepatitisVirusesAll cases and outbreaks associated with consumption of raw or improperly cooked molluscan shellfish9Food safety aspects• Scombroid poisoning– Consumption of fish of the family Scombridae• Tuna, mackerel• Also some non-scombroid fish– Sardines, herring• Histidine converted to histamine–Symptoms• Flushing of skin, headache, diarrhea, body rash, shortness of breath, blistering of mouthFood safety aspects• Scombroid poisoning– Control measures• Proper harvesting and post-harvesting practices (cooling)•Regulation– ≤5 mg histamine/100 g (50 ppm) - regulatory action– ≤50 mg histamine/100 g - health hazard– Most common in U.S.• Mahi mahi, tuna, bluefishFood safety aspects•Ciguatera– Intoxication from fish such as barracuda, grouper and red snapper that have ingested toxic dinoflagellates, such as Gambierdiscustoxicus.– In the U.S., usually fish from tropical or semi-tropical regions10Food safety aspects•Ciguatera–Symptoms• Vomiting, diarrhea, itching, burning sensation of tongue, alternate hot and cold sensations (within minutes to hours)– Toxin heat stable– 2 to 7% fatality rateFood safety aspects• Paralytic shellfish poisoning– Consumption of shellfish (oysters, mussels, clam) that have ingested certain dinoflagellates, primarily Gonyaulaxspp– If concentration of saxitoxin is ≥80 µg/100 g, harvesting is prohibited–Symptoms• Tingling and numbness around mouth after 1 h•Death by respiratory failure in extreme casesFood safety aspects• Amnesic shellfish poisoning– Shellfish containing domoic acid• Believed caused by plankton blooms– Onset 30 min to 24 h after ingestion–Symptoms• Temporary loss of short-term memory, nausea, vomiting, abdominal cramps, diarrhea and anorexia– FDA action level - 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