L3 Food Poisoning & Spoilage 2024 PDF

Lecture 3 Food Poisoning and Spoilage FNSC5430/LSCI6843 Food Toxicology and Safety Gordon Cheung B.Sc.(Hons.), Pg.D. Diet., M.Phil., Cert. Chi. Med., R.D.(UK)  Content Food poisoning Bacillus cereus...

Lecture 3 Food Poisoning and Spoilage FNSC5430/LSCI6843 Food Toxicology and Safety Gordon Cheung B.Sc.(Hons.), Pg.D. Diet., M.Phil., Cert. Chi. Med., R.D.(UK)  Content Food poisoning Bacillus cereus Vibrio parahaemolyticus Clostridium botulinum Escherichia coli O157 Clostridium perfringenes Viruses (Hepatitis A and Norwalk Escherichia coli viruses etc.) Salmonella Staphylococcus aureus Food poisoning in Hong Kong Management of food poisoning outbreak Food deterioration, food spoilage and unfit food FAO / WHO Pan European Conference on Food Safety February 2002 “Foodborne disease caused by microbiological hazards is a large and growing public health problem” “Most countries with systems for reporting foodborne disease have documented significant increases”  Types of Food Poisoning Mycotoxins Poisonous Marine toxins Chemical Metallic plants/fish Infectious Bacterial Toxic Salmonella spp. Clostridium perfringens Vibrio parahaemolyticus Staphylococcus aureus Yersinia enterocolitica Bacillus cereus Clostridium botulinum Infectious and toxic Escherichia coli  Food-Borne Disease Food-borne disease differs from food poisoning A relatively small number of organisms is capable of causing the illness The food acts purely as a vehicle and the multiplication of the organism within the food is not an important feature of the illness  Food Poisoning Bacterial Food Poisoning: An acute disturbance of the gastrointestinal tract resulting in: Abdominal pain With or without diarrhoea and vomiting Due to the consumption of food contaminated by specific pathogenic bacteria or their toxins  Food Poisoning -High Risk Foods Cooked meat (“siu mei” and “lo mei”) Milk, cream, artificial cream and dairy products e.g. frozen confections) Eggs and egg products e.g. sandwiches Shell fish or seafood e.g. oyster, sushi and sashimi Cooked rice Bulk production food such as buffet, poon choi and lunch boxes  Food Poisoning Essential terminology: At risk groups Incubation periods Onset time Implicated foods Symptoms Infective dose Vehicle of infection Conditions for growth It can be classified into 2 categories: Caused directly by the invasion of the body by bacteria (infection) Caused by bacterial toxins produced either directly on the food or produced in the body after ingestion (intoxication)  Bacterial Toxins Endotoxins: Sealed within the bacterial cell Released only when the bacterium dies or sporulates This may occur either before or after the food is consumed Clostridium perfringens – sporulate in the intestine Exotoxins: Secreted during binary fission or as digestive waste products Contamination of food can occur before it is eaten Cooking may kill the bacteria but the exotoxin will still be present and can cause illness  Bacterial Toxins Enterotoxins: Affect the intestine Virulently poisonous Neurotoxins: Most dangerous biotoxins known Clostridium botulinum  Food Poisoning Symptoms include – abdominal pain, diarrhoea, vomiting, fever, malaise Short incubation period ( 6hrs -72hrs) Numbers of bacteria will affect the incubation period Recovery period varies ( 6hrs to 1 week) Important Contributing Factors in Hong Kong Contamination Cross contamination of ready-to-eat food by raw food Contaminated raw food Poor personal hygiene Inadequate cleaning of equipment Contamination by food handlers e.g. hands, cloths and equipment Temperature Inadequate cooking/ reheating Inappropriate storage temperature Inadequate cooling and cold holding Time Prolonged storage Preparing food ahead of planned service  Major Contributing Factors UK 50% inadequate cooking or re-heating 45% food stored inappropriately 39% cross contamination 12% infected food handler US Food from unsafe sources Inadequate cooking Improper Holding Temperatures Contaminated equipment Poor personal hygiene  Why Food Poisoning Happens? Lack or training / awareness? Negligence? Inadequate management? Lack of appropriate equipment? Inappropriate food handling which the business is ill-equipped to deal with? Microbiological Agents Causing Food Poisoning  Food Poisoning – Bacillus cereus Implicated foods – cereals and grains, Recognized in early 1900’s rice and rice based items, meat, fish, First reported outbreak 1970’s milk, vegetables, pasta, soya beans Aerobic, gram-positive, spore former Common route of infection - cooking of Soil, dust, vegetation boiled rice, stored at ambient temperatures allowing spores to Growth range: 7C – 48C; optimum is germinate and produce a toxin. between 28C – 35C Reheating does not destroy the toxin Production of two toxins Control – strict temperature/time regime - cooling - storing - reheating  Food Poisoning – Clostridium botulinum Infection route is through raw food Recognised in late 18 century in contaminated with spores. Following German sausages germination the multiplying bacteria produce an Rare but severe exotoxin Anaerobic, Gram-positive, spore forming rod Neurotoxin – double vision, difficulty in speaking and swallowing, respiratory failure Soil and water Seven species identified – 5 IP: 8 – 72 hrs, 12 – 36 typical cause disease in humans, 2 Illness lasts 24hrs – 10 days, mortality rate >60% species associated with animals Poor competitor – cannot grow in the presence of other organisms  Food Poisoning – Clostridium perfringens Recognised in early 1950’s Anaerobic, Gram-positive, spore-forming rod Five types: type A most recognised with food- borne illness Sources: human and animal intestine, soil, dust and spices Illness is caused by an enterotoxin when large numbers (1m) sporulate in the intestine  Food Poisoning – Clostridium perfringens Usually occurs as a consequence of bad food-preparation practices Symptoms: diarrhoea and abdominal Spores form as a survival response to the pain. Vomiting rare “threat” of heat while food is cooking IP: 6 - 24 hrs ( norm 8hrs – 12hrs) If the food cools slowly, spores Illness lasts > 48hrs germinate and bacterial multiplication occurs Latest research suggests the toxin can be produced in the food itself resulting in In the intestine, spores form again shorter onset times releasing a enterotoxin which causes an illness  Food Poisoning – Escherichia coli Normal inhabitant of human and animal Used as an indicator organism for faecal intestines contamination of food or water Aerobic most being harmless commensals Common foods: raw meat, undercooked Enterotoxic E. coli (ETEC) most meat products, gravy and raw milk common causing severe abdominal pain Mesophilic organism, 7oC – 10oC and and diarrhoea can survive refrigeration temperatures IP: 12 – 24 hrs, enterotoxin Optimal temperature is 37oC Symptoms: abdominal pain, fever, diarrhoea, vomiting Control: safe disposal of sewage, Illness lasts 1 – 5 days separation of raw and cooked foods, Source: human / animal intestine, meat adequate cooking and effective personal and sewage hygiene  Food Poisoning – Salmonella New strains described every year Symptoms: diarrhoea, vomiting, fever Antibiotic resistant strains and abdominal pain, lasting > 7 days Main reservoirs – humans and animals 5% become carriers 3000 serotypes divided into three groups Preferred conditions: 7oC – 45oC Salmonella Typhimurium and S. Sources: human and animal intestinal Enteritidis most common causes of food tracts and faeces poisoning Infection route is via raw animal Illness caused by a large invasion of products such as raw meat, eggs, milk bacteria which have multiplied in the and poultry, vegetables, insects, birds, food. rodents sewage and water IP: 6 – 72 hours (norm 12 – 36 hrs) Control: high standards of food production, effective pest control  Food Poisoning – Staphylococcus aureus First identified late in 18th century Anaerobic, mostly resident in humans Onset time: 1 – 6 hours, lasting 24 – 48 Source: nose, throat, hair, skin, hands, hours boils, pimples, burns and wounds Growth range: 7oC – 48oC, with toxin Exotoxin producer, 1m bacteria per produced between 10oC – 45oC gram of food to produce sufficient toxin Sources: ham, poultry, egg products, for symptoms dairy products, potato salads, raw milk Toxin is heat resistant and can survive 30 Control: infection is via humans and minutes at 100oC poor hygiene practices – infected food Symptoms: diarrhoea, acute vomiting, handlers contaminate the food via poor nausea, abdominal pain personal hygiene  Food Poisoning – Vibrio parahaemolyticus Halophilic bacteria, usually exist in Sources: usually sea foods including fish, marine environment and mostly grow on crustacean, shellfish, jelly fish etc. fishes and shellfish Improper food handling may leading to cross contamination of other foods such Grow well in environment with 3% - as siu mei and lo mei 3.5% sodium chloride concentration and sensitive to acid Mode of transmission: Consumption of raw or not thoroughly cooked sea foods Can be killed by cooking at 75oC that are contaminated IP: 4 to 30 hours, usually 12 to 24 hours Prevention: avoid cross contamination of Symptoms: nausea, vomiting, diarrhoea, raw and cooked food, good food abdominal pain, fever, headache, thirsty production and avoid consumption of and perspiration raw or not thoroughly cooked sea foods  Food Poisoning - Listeria monocytogenes Six species, anaerobic organism Tolerant to salt but not a spore former Known and documented for several Psychotropic – able to grow at 1oC – decades 3oC L. monocytogenes most concern Poses special problems for handling and distributed in: soil, water, sewage storage – refrigeration Excreted by human and animal carriers IP: 24hrs – 70 days (norm 21 days) and cross-infection is common Symptoms: fever, septicaemia, meningitis Associated with chilled or delicatessen Healthy adults are highly resistant and products – soft cheeses, pate, cook-chill may only show mild flu symptoms meals, coleslaw, prepared salads, fruits At risk groups – pregnant women and and vegetables foetuses resulting in still births  Food Poisoning - Viruses Viruses are typically water borne Much smaller than bacteria and highly Contamination at source (food eaten raw) infectious – one third smaller than bacteria and by handling No complete cell structure and cannot reproduce independently – can only Normal cooking temperatures denatures multiply within a cell viruses 2000+ reported cases annually – true rate Raw foods most implicated in outbreaks far higher Examples include: Infective dose very small – can be a single Hepatitis A virus Norwalk (Norovirus) Very contagious and person to person Rotavirus spread is common and typical of outbreaks Remember – food /water borne and do not Spread by faecal – oral route require the food/water for multiplication Onset of illness is sudden and often “explosive”  Norwalk-like Virus Small round structured viruses Source: human intestine and sewage contaminated water IP: 1 – 2 days, illness lasts 1 – 3 days Implicated foods: shellfish, vegetables, salads and water Symptoms: nausea, vomiting, diarrhoea and abdominal pain Control: same as HAV  Food Poisoning Outbreaks in HK Statutory notifiable disease in HK since March 1974. The Centre for Health Protection (CHP) of Department of Health conducts surveillance and investigation of food borne diseases. Definition by CHP An incident in which two or more persons experience a similar illness after ingestion of a common food, and epidemiological analysis implicates the food as the source of the illness. (Exception: one case of botulism, chemical poisoning or biochemical poisoning constitutes an outbreak.) No. of Food Poisoning Outbreaks Related to Food Premises and Food Business and the Corresponding no. of Persons Affected in HK (2013-2022)  Common Food Involved in Hong Kong Siu Mei + Lo mei Poon choi Sushi + sashimi Buffet & lunch boxes Oysters Seafood Hotpot Salad  Causative agents of FP in 2022 9% 24% 67% Bacteria Viruses Biochemcial Management of Food Poisoning Outbreaks Epidemiological information from CHP Conduct field investigation Implement control measures Environment Food Person  Field Investigation Public health doctor and nurse from Food Incidents and Response Management (FIRM) work with Health Inspector of Environmental Hygiene Branch (EHB) as a team  Why to Investigate? Control/prevention Prevent further outbreak Assess population at risk and implement control measures Research opportunities Gain additional knowledge Opportunity to study natural history of the disease Newly recognized disease Training opportunity for epidemiologists Public, political, or legal concerns  Outbreak Investigation Taking into account of the epidemiological findings, carry out investigation & identify possible causes: Environment Inspect general hygiene and identify irregularities. e.g., Cross contamination of food (e.g., utensils, working area for raw & cooked food) Facilities (e.g., temperature of fridge & bain-marie) Infestation (e.g. rodent & cockroach) Collect environmental samples for testing  Outbreak Investigation Food Condition and duration of food storage Holding temperature Risk of cross contamination (e.g., improper storage of raw and ready to eat food) Collect food samples for testing  Raw meat Cold dish  Field Investigation – Food Processing and Handlers Food processing Inquire food preparation steps Note the critical control points in the preparatory process Note the serving volume and food variety Food handler Inquire staff movement/ employment of part-time staff Inquire the job duties of food handlers Inquire medical symptoms or carrier state Test knowledge & attitude on hygienic practice Collect samples for laboratory testing e.g. wound swabs, nasal swabs, stool specimens Field Investigation – Source of Incriminated Foods Trace the source and distribution of incriminated food For further control measures by collaborating with local traders and exporting countries Examples: July 2006: over 30 food poisoning outbreaks in 8 restaurants affecting > 80 persons related to consumption of raw sea urchins from the same supplier Sep – Oct 2006: over 10 food poisoning outbreaks in 4 food premises affecting 44 persons related to consumption of raw oyster from one supplier  Implement Control Measures Rectifying irregularities Cleansing & disinfection Disposal of incriminated food Health advice on food safety Health talk for food handlers Surrender of incriminated food  Implement Control Measures If indicated, suggest more stringent control measures Stop sale of certain high risk food / food recall Verbal warning Summons action Demerit point systems Suspension of food handlers Suspension of food business Closure of food premises Public announcement  5 Keys to Food Safety Advocated by the World Health Organization to prevent foodborne diseases (3C+2S) 1. Choose (Choose safe raw materials) 2. Clean (Keep hands and utensils clean) 3. Cook (Cook thoroughly) 4. Separate (Separate raw and cooked food) 5. Safe Temperature (Keep food at safe temperature) Food Spoilage and Unfit Food Food Deterioration, Food Spoilage and Unfit Food Food deterioration can be defined as the gradually lowering of food quality over time The food is considered spoiled when the deterioration becomes so advanced that it is organoleptically unacceptable A spoiled food is usually unfit for human consumption  Spoilage Spoilage is the undesirable organoleptic change (decay or decomposition) of food, which may be caused by: Microorganisms Pests Natural enzymatic actions of plants/animals (breakdown proteins, carbohydrates and fats and cause spoilage) Chemical reactions, e.g. oxidation of fat resulting in rancidity Physical changes, such as those caused by temperature (both heat and cold), moisture (hygroscopicity and drying), air (particularly, oxygen), light etc  Microbial Association in Spoilage of Food Deterioration of a food is actually caused by only a small proportion of the normal flora initially present on it When environmental conditions (such as temperature, humidity, light, water etc.) favour, microorganisms will continue to proliferate Decomposed products which render the food unfit for human consumption are commonly known as poisons or toxins Microorganisms leading to spoilage are mainly bacteria, yeast and mold Bacteria Divided into 2 groups, spore forming and non-spore forming Usually prefer to grow in low acid food such as vegetables and meat  Microbial Association in Spoilage of Food Yeast Divided into true yeast and false yeast Growing of yeast will lead to fermentation Can grow in foods with high acidity True yeast will metabolize carbohydrates producing alcohol and carbon dioxide gas False yeast prefer growing on the surface of high acid food with high sugar content, and will create a dry film on the food surface Mold Will form obvious fine silk-like filaments Spore forming Grow in foods with high acidity  Signs of Food Spoilage Aerobic food spoilage Limit to surface of food Food spoiled by mold like some cheese is still fit for consumption when moldy part is removed However, if there are enormous growth of bacteria on its surface, bacteria may have infiltrate into the core of food producing toxins Anaerobic food spoilage Happen at internal part of food or food contain in hermetically sealed containers (such as can) Caused by anaerobic bacteria Will produce organic acid, turning the food sour Will produce gas e.g. carbon dioxide  Detection of Food Spoilage By sensation By Laboratory Smell Aerobic Plate Count Visual inspection Anaerobic Plate Count Organoleptic Total coliform count Feeling Psychrotrophic Plate Count Mesophilic aerobic / anaerobic spore formers Thermophilic aerobic / anaerobic spore formers Yeast & Mold count  Unfit Foods “A product is fit for food if a discriminating consumer, knowing the story of its production and seeing the material itself, will eat it, and conversely, the same product is spoiled when such an examiner refuses it as food.” Three aspects when judging fitness of food: Nutritional value Safety Aesthetic aspects such as odour, appearance, colour etc.  Unfit Food Overripe fruit or vegetables may usually regard as unfit not only because of the adverse change in taste, texture and colour, but also the loss of expected shelf-life. Overcooked food in general cannot be regarded as unfit, though they are of lower quality. The time a food becomes unfit for human consumption is a question of fact in each case  Unfit Food Harmless inert matter inside a food was held not unfit: A small piece of metal in a cream bun was held NOT unfit: A piece of string in a loaf of bread was held NOT unfit: Putrid or decomposed and unwholesome conditions. A food was held unfit under the following circumstances: A used and dirty bandage in a loaf of bread was held unfit: A small amount of harmless mold (Penicillium) on a pie was held unfit even though that it was not hazardous to health: Food contaminated by antibiotics or pesticides is fit or unfit to be determined by scientific evidence Action may be taken under section 52 and 54 “not of the substance” (demanded by the purchaser)  Examples of Unfit Food Putrid or decomposed food. Rancid food. Food with radioactivity exceeding 600 Cooked or ready to serve food Bq. containing the bacteria Listeria monocytogenes. Meat infected with Cysticercus cellulosae, C. bovis. Food which has been confirmed by laboratory tests to have caused food Carcass or offals condemned for poisoning. septicaemic or tuberculosis. Blown cans (unless proved otherwise). Puffer fish (unless proved otherwise, for instance by a health certificate). Food containing salicylic acid. Fish or shellfish with a toxicity > 4000 Food containing boric acid exceeding M.U/kg 3000 ppm