Seafood & Fermented Foods Lecture 8 PDF

Seafood & Fermented Foods ENH 333 – Introduction to Food Hygiene Lecture 8  Seafood Refers to fish, crustaceans, and mollusks from fresh and marine waters One of the most perishable of all protein-based foods – Regularly linked to food-borne diseas...

Seafood & Fermented Foods ENH 333 – Introduction to Food Hygiene Lecture 8  Seafood Refers to fish, crustaceans, and mollusks from fresh and marine waters One of the most perishable of all protein-based foods – Regularly linked to food-borne disease Microbiota of healthy fish is reflective of their source waters As with meat, inner tissues of healthy fish are generally sterile pre-harvest – However, shellfish can be contaminated from harvest waters (e.g. fecal pollution or natural biota) Post-harvest, fish flesh can become contaminated through gutting, filleting and other processing/handling  Seafood Microbiota can be found on the outer slime, gills and intestines, and can include: – Bacteria = e.g. Aeromonas, Pseudomonas, Shewanella, Moraxella, Vibrio – Yeasts = e.g. Candida, Cryptococcus, Rhodotorula, Sporobolomyces – Moulds = e.g. Aspergillus, Aureobasidium, Penicillium Seafood spoilage is affected by: – Type and species (composition) – Contamination level at point of harvest – Temperature of storage – Physical condition – Treatment of the product (e.g. washing, evisceration)  Seafood Spoilage Fresh fish are spoiled by bacteria – salted / dried fish are spoiled by fungi Bacterial spoilage is largely due to Gram-negative, non-spore formers Many fish-spoilage bacteria can grow at refrigeration temps The spoilage of freshwater and saltwater fish occurs in the same way The most susceptible part of the fish is the gills – the earliest signs of spoilage can be seen in the gill region  Seafood Spoilage Trimethylamine – N – oxide (TMAO) is naturally present in fish – Is broken down to trimethylamine (TMA) by microbial action TMA gives the characteristic “fishy” odour of spoiled fish TMA has been used in detecting fish spoilage Other metabolites produced during fish spoilage include: – CO2, ethanol, propanol, isopropanol, histamine and various volatile materials such as volatile organic acids and total volatile nitrogen In addition, the unsaturated oils in fish are more easily subject to oxidization – rancidity  Seafood Spoilage Detection Smell – Freshly caught fish have very little odour – Time to develop “fishy” odour varies with species – Odour from trimethylamine (TMA) and rancid oils Surface Slime – Normal fish scales are coated with a thin, clear, slippery mucus – Deterioration causes mucus to thicken, discolour and develop an objectionable odour – A sticky / tacky feel to fish means that they are not fresh Flesh – Softens over time – Should be “springy”  Seafood Spoilage Eyes Fresh - bright, convex Stale - dull, collapsed Blood Fresh - bright red Stale - dull red to brown in gills and along spine Colours Faded Yellow, green, brown discolourations appear  Crustaceans Includes shrimp, lobsters, crabs, and crayfish Susceptible to many of the same spoilage organisms as fish Crustaceans are commonly sold live – from tanks in restaurants or supermarkets Can be cooked on premises, pre-cooked or live During inspections – look for dead animals in the tank – these should be removed and not sold Because of the high nitrogen levels, these will spoil quickly and contaminate the tank  Mollusks Includes oysters, clams, mussels and scallops Spoilage can be determined by pH decrease – 5.9-6.2 is good, 5.8 is “off”, 5.5-5.7 is “musty”, any less is sour or putrid One major issue with this group is that they are filter feeders – they filter water to remove food particles As well as filtering water for food, they also remove all other particles – including microorganisms If mollusks are exposed to contaminated water they can filter the water and concentrate any pathogens present within their own bodies What to Look for during Inspections Fresh Whole Fish Fresh, mild odour Firm flesh Fresh Whole Shellfish Fresh, mild odour Shell, tightly closed shells Fresh Fillets Glossy, firm / elastic flesh No discolouration Well iced  Seafood Legislation: Federal Fish and seafood products that are processed in federal establishments or imported into Canada are regulated under the Safe Food for Canadians Regulations, including: – Licensing of establishments – Grading requirements E.g. Pacific Salmon can be graded as Grade A, Standard or Utility – Labelling and packing – General food safety provisions, including a preventive control plan (previously called a “Quality Management Program” in this industry) – Import restrictions (e.g. mitten crab)  Canadian Shellfish Sanitation Program The Canadian Shellfish Sanitation Program (CSSP) is a federal food safety program jointly administered by the Canadian Food Inspection Agency (CFIA), Environment Canada (EC) and Fisheries and Oceans Canada (DFO) – The goal is to protect Canadians from the health risks associated with the consumption of contaminated bivalve molluscan shellfish CFIA roles include: – Regulating the import and export and all processing operations including inspection and certification – Maintaining a biotoxin surveillance program of shellfish growing areas EC monitors the sanitary quality of shellfish growing areas DFO controls the harvesting of shellfish and restricts harvesting from contaminated areas Canadian Shellfish Sanitation Program The shellfish sanitation program covers: – Shellfish area survey and classification – Control of harvesting – Harvesting, handling and storage of shellstock – Shucking and packing shellfish – Policy and procedures for controlled relaying and depuration: Decontamination methods for operators who are licensed under the Management of Contaminated Fisheries Regulations to harvest shellfish from contaminated areas Emergency closures of harvesting areas can occur due to: – Significant weather events (e.g. heavy rainfall) – Other unexpected events (e.g. oil spill) Video: Shellfish depuration process https://www.youtube.com/watch?v=uSYDkd8 mZ9c  Shellfish Sanitary Contamination Closures https://inter-w01.dfo-mpo.gc.ca/Geocortex/Essentials/Viewer/Index.html?viewer=CSSP_Public_En_Site http://www.bccdc.ca/health-professionals/professional-resources/shellfish-harvesting-sites-status-map  CFIA Depuration Requirements Pre-depuration – Time between harvest and depuration should not exceed 3 days – Shellfish are washed and culled to remove dead, broken, or cracked shellfish prior to depuration Depuration process – Water must have 300 fishes (e.g. barracuda, grouper, moray eel, sea bass) that feed on herbivorous or reef fishes, which in turn feed on phytoplankton (dinoflagellates) The dinoflagellate Gambierdiscus toxicus produces ciguatoxin Toxin concentrates in fish liver, intestines, roe, and heads Symptoms occur within 3-6 hrs and include nausea, vomiting, abdominal pain and diarrhea followed by neurologic symptoms that can last days to weeks, such as: – Prickling of the mouth, tongue, and throat; headaches; muscle soreness; sensation that the teeth are loose; itching; metallic taste; temperature reversal (hot things feel cold and cold things feel hot); blurred vision; or even transient blindness Ciguatera Poisoning  Shellfish Poisoning Caused by a group of toxins produced by planktonic algae (dinoflagellates or diatoms) that shellfish feed on, harvesting must monitor for potential biotoxins Paralytic Shellfish Poisoning (PSP) – Caused by saxitoxins produced by dinoflagellates from the Alexandrium and Gymnodinium genera – Includes neurological symptoms (e.g. tingling, burning, numbness) that develop within 2 hrs and can be severe (e.g. incoherent speech, respiratory paralysis, death) Amnesic Shellfish Poisoning (ASP) – Rare form of poisoning associated with mussels contaminated with domoic acid, produced by the diatom Nitzchia pungens – Causes gastroenteric and neurologic symptoms within 24-48 hrs; the latter can be severe in elderly patients  Shellfish Poisoning Diarrhetic Shellfish Poisoning (DSP) – Caused by toxins that include polyether molecules (e.g. okadaic acid) produced by dinoflagellates – Usually mild GI illness (nausea, vomiting, abdominal cramps, diarrhea chills) that occurs within 30 min to 3 hrs and can last 2-3 days Neurotoxic Shellfish Poisoning (NSP) – Caused by brevetoxins produced by dinoflagellates in shellfish harvested along the Florida coast and Gulf of Mexico – Causes gastroenteric and neurologic symptoms within mins to hrs, including tingling, numbness, muscle aches, reversal of sensation of hot and cold, diarrhea, and vomiting – Symptoms lasts several hours to days http://time.com/5264704/raw-oysters-norovirus-outbreak/  Raw Oyster Consumption Raw oysters have caused numerous food-borne disease outbreaks of the past several years, often due to norovirus and Vibrio spp. Consumption of raw oysters is not encouraged, especially for vulnerable groups – Oysters that are pre-shucked (usually sold in tubs) should not be eaten raw Oysters need to be cooked to an internal temperature of 90°C for 90 s to kill norovirus The following are recommended cooking methods for oysters and other shellfish (e.g. clams, mussels): – Boil until shells open, then for an additional 3-5 minutes – Steam for 4-9 minutes and throw out those that do not open – Fry for at least 3 minutes at 190°C – Bake for at least 10 minutes at 230°C  Fermented Food Products Fermented foods = foods in which chemical changes are brought about through the action of enzymes elaborated by microorganisms – Is a metabolic process in which a microorganism converts a carbohydrate such as starch or sugar into alcohol and/or acid Renewed interest in fermentation due to its ability to preserve foods and extend shelf life, create new flavours/textures, and real or perceived health benefits Example products: Salami, Cheese, Butter, Yogurt, Sauerkraut, Kimchi, Pickles, Olives, Kombucha, Tempeh, Miso, Beer, Wine, Bread  Biochemical Foundation When a compound is oxidized, it loses an electron, which must “go” somewhere (usually an electron acceptor, which becomes reduced) Complete oxidation of sugar produces energy which is stored in the form of compounds such as adenosine triphosphate (ATP) Food fermentation usually occurs under anaerobic conditions, where there is no oxygen present to accept electrons from the oxidized sugar, so part of the sugar must serve as the electron acceptor – The incompletely oxidized fermentation products (e.g. ethanol, acetic acid, lactic acid) are sometimes oxidized by other “salvaging” microorganisms  Biochemical Foundation Simplified catabolic pathways used in fermented foods: Source: Montville, 2008 https://www.theglobeandmail.com/life/health-and-fitness/health-advisor/fermented-meats-are-good-for-you- and-they-even-taste-good-too/article27941523/  Fermented Meat Products The natural microbiota of meat is gram-negative, aerobic putrefying spoilage bacteria – Fermentation of meat by lactic acid bacteria (LAB) prevents spoilage and turns the meat into a different product Although some manufacturers still depend upon naturally occurring microbiota to ferment meat, most now use starter cultures of single species or combinations of species of LAB and/or staphylococci – Starter cultures have been selected for their metabolic activities especially suited for fermentation in meat ecosystems – Helps to ensure a more consistent product and shortens the processing time Most common products are dry and semi-dry sausages  Fermented Sausages The manufacture of dry and semi-dry sausages involves the following general steps: – Reduce particle size of high-quality meat by grinding – Add salt (2.5-3%), nitrate or nitrite (100-150 ppm), glucose as a fermentable sugar, spices, and starter culture at 107 CFU/g Nitrate/nitrite inhibits C. botulinum, contributes to the cured meat taste, and converts myoglobin to nitrosomyoglobin – Blend the ingredients – Vacuum stuff the meat into the casing – Incubate (also referred to as “ripen”) the sausages – starter cultures reduce pH to 50%) of the business is food service (i.e. preparing and serving meals) Licensed meat plants that produce fermented meats must meet similar requirements as federal facilities, and are regularly inspected by OMAFRA inspectors OMAFRA has a microbiological monitoring program in meat plants that produce ready-to-eat meat products – If unacceptable results are obtained, CFIA conducts risk assessment and other necessary actions (e.g. product recall) https://news.ontario.ca/omafra/en/2017/07/woodbridge-company-fined-under-food-safety-legislation.html  Fermented Dairy Products There are various fermented dairy products (e.g. butter, buttermilk, yogurt) – These products are fermented by lactic acid bacteria (LAB) Since pasteurization kills most of the natural LAB, starter cultures need to be added – Starter cultures always include bacteria that convert lactose to lactic acid (e.g. Lactococcus lactis subsp. cremoris or lactis) – Other bacteria, referred to as the secondary microbiota, are added to some fermented products to influence flavor and texture (e.g. Leuconostoc species) – The acidified product is usually the start point for the manufacture of various products LAB cultures inhibit the growth of pathogens  Butter and Yogurt Butter and buttermilk LAB culture added to pasteurized cream and held until desired acidity is reached Acidified cream is churned to separate solids and buttermilk Yogurt Milk is first heated to reduce water Then Streptococcus thermophilus and Lactobacillus bulgaricus are added in 1:1 ratio at level of 2% by volume – Probiotic yogurts also contain Bifidobacterium or L. acidophilus The coccus grows faster and produces initial acid, while the bacillus produces flavour compounds (chiefly acetaldehyde) Product contains 109 cfu/g LAB – decreases during shelf life  Cheese There many different varieties of cheeses, which are classified by their texture, moisture, milk type, ripening procedure The general process for producing cheese is as follows: 1. Milk is often standardized (optimizing protein-fat ratio) before cheesemaking to improve the yield and quality of the product 2. The milk may be heat-treated/pasteurized to kill spoilage organisms and improve the environment for the starter cultures to grow 3. The milk is brought to a temperature of 30-32°C (optimal for starter cultures)  Cheese 4. Starter culture is added and ripening occurs – Most cheeses are ripened by LAB; some are ripened by moulds (e.g. brie) and some are unripened (e.g. cottage cheese) – Ripening occurs rapidly (within hours), lowing the pH and developing the flavor of the cheese 5. Rennet enzyme is added to coagulate milk proteins, forming curds 6. Curd ferments (raising pH), then is cut and heated, whey is separated, and curd it salted and pressed into blocks 7. Other ingredients may be added, then cheese is “aged” for several weeks to many years  Video: Cheese Processing https://www.youtube.com/watch?v=LAZHwix xx88  Dairy Product Spoilage Butter can be spoiled by moulds and yeasts that grow on the surface producing discolourations – Can also be spoiled by bacteria (e.g. Pseudomonas spp.), resulting in: surface taint (putridity), rancidity, malty flavor, and skunk-like odours Cottage cheese can be spoiled by bacteria (causing “slimy curd”) or moulds and yeasts (causing stale, musty, moldy, yeasty flavours) Soft, unripened cheeses are susceptible to mould growth when oxygen is present – Usually caused by Penicillium spp. – Hard and semi-hard cheeses are less susceptible to spoilage due to their low moisture content  Cheese: Food Safety Concerns Soft cheeses and cheeses made from unpasteurized milk have caused numerous outbreaks of food-borne illness over the past several decades – Most are caused by Salmonella and Campylobacter – Main contributing factors are contaminated raw product from animals or the environment and insufficient time/temperature control Pasteurized milk cheeses have also caused several outbreaks: – Most are caused by Listeria and norovirus – Main contributing factors include improper cleaning, storage, food handling, and worker hygiene Health Canada recommends that high-risk groups avoid consumption of all soft cheeses to reduce their risk of illness  Sauerkraut Fermented cabbage – produced via the normal microbiota (lactic acid bacteria) Addition of 2-2.5% salt to shredded cabbage inhibits Gram- negative bacteria – allowing the fermentation to occur – A suitable fermentation vessel should be used (e.g. glass jars, food- grade heavy plastic, or new ceramic crock) – avoid metal, non-food- grade plastic and old ceramic crocks (the latter may contain lead) – To create an anaerobic environment, the cabbage needs to be covered At 21-24°C, fermentation will take 3-4 weeks Process takes longer at lower temperatures, but may not ferment at 24°C may cause spoilage Final pH should be 3.1 to 3.7, with acidity 1.6-1.8%  Sauerkraut Spoilage in sauerkraut causes undesirable colour, off-odours, soft texture and unpleasant flavor – May be unsafe to eat if insufficient acid has been produced Due to the high acidity, finished kraut is generally spoiled by surface growth of moulds – Some surface spoilage can be removed and the product below can be used, but the pH should be checked to confirm a safe level Other types of spoilage could include: – Softness = bacterial growth due to insufficient salt, high temperatures during fermentation, uneven salt distribution or air pockets – Rotted kraut = surface growth of microorganisms due to insufficient exclusion of air during fermentation – Pink kraut = growth of yeasts on the surface  Pickles Pickles are fermentation products of fresh cucumbers – Fermentation occurs via the normal microbiota (lactic acid bacteria) The commercial process involves placing cucumbers in large brine tanks at salt levels of 6% for 6-9 weeks – The salt inhibits undesirable Gram-negative bacteria and extracts water/other compounds (e.g. sugars) from the cucumbers which are converted to lactic acid – the final pH is around 3.7 to 4.0 – Home fermentation method is similar to sauerkraut Excessive carbon dioxide or bacterial growth can cause “bloaters” (undesired gas pockets) Spoilage can include blackening (bacteria) and softening (various microbes) http://www.wsj.com/articles/SB10001424052970204879004577108632273070376  Kimchi Traditional Korean dish made of fermented radish, cabbage or cucumber, with a mixture of other ingredients (e.g. green onion, ginger, garlic, red pepper) and seasonings Formation of organic acids (primarily lactic and acetic acid) results in an optimum pH of 4.2, restricting pathogen growth Ferments at room temperature in only 1-2 days, or more slowly in the refrigerator Is best eaten within 1 week, and may require refrigeration (depending on pH) Has caused numerous outbreaks among school children in Korea  Kimchi Napa Cabbage Rinse and drain under cold water Chop into 2-inch pieces Salt Cabbage Soak in saltwater solution (15%) for 3-6 hours Rinsing and draining of excess water (30 min) Prepare and Add Seasonings E.g. minced garlic and ginger, shredded radish, green onions, red pepper powder Pack Container Pack tightly to 2/3rd full If using jars, seal to finger-tip tight Ferment Option 1: In refrigerator slowly over 2-3 days Option 2: 1-2 days at room temperature (20°C is ideal) Adapted from: CSU, 2016: http://farmtotable.colostate.edu/prepare-ferment/kimchi.php#.V8iEtCgrKhc  Tempeh Tempeh is a fermented soybean product that is used as a meat alternative – Has a chewy texture and earthy flavour – Fermentation process gives product a higher content of protein, dietary fiber, and vitamins It is produced by inoculating cooked and dried soybeans with Rhizopus mould and fermenting in tightly packed containers for 20-28 hours at 31°C – During fermentation, mould growth occurs and binds the beans together as a cake An outbreak occurred in 2012 in the US from contaminated starter culture  Kombucha Kombucha is a fermented beverage made from brewed tea and sugar – Has a slightly sweet and acidic taste, with residual carbon dioxide – Is consumed in many countries as a health beverage, with growing popularity in North America Fermentation process resembles that of vinegar, with a “symbiotic culture of yeasts and bacteria” (i.e. SCOBY), at room temperature for 7-10 days SCOBY Final pH should be in the range of 2.5 to 4.2, with alcohol and acetic acid content