Food Contamination Study Handouts

Source of contamination • Air, Water, plant, soil, food handler, machinery and equipment, sewage and trucks or carts during transport Contamination of food results in its spoilage 58 Food contaminants • Biological – – • Chemical – – – • micro-organisms: bacteria, viruses and parasites naturally occurring chemicals in some fungi (such as moulds), plants, fish and shellfish cleaning chemicals pesticides unsuitable metal containers Physical – – – – broken glass hair, fingernails stones, leaves paper, packaging 59 29 Types Of Food Contamination. MICROBIOLOGICAL: - Bacteria - Moulds CHEMICAL: - Pesticides - Cleaning chemicals PHYSICAL: - Glass & hard plastic - Bones / hairs - Plasters - Viruses - Parasites - Insecticides - Metal - Cigarette Ends - Insects 60 Sources of physical, biological and chemical contaminants • • • • • • • • • • • Physical People Packaging Raw food and the natural environment Buildings and equipment Pests Chemical Cleaning products Products used in agriculture Pest control products Metals 61 30 Sources of biological contaminants • Animals • Raw foods, such as – – – – • • • • • meat and poultry Fish eggs vegetables Water Air and dust People Pests Dirt, rubbish and waste food 62 Routes of contamination A) Primary source,i.e. Man, through the 1) Respiratory tract 2) Infected Skin 3) Intestinal tract B) Secondary Source,i.e. Intermediates, such as: 1) Contaminated equipment and utensils 2) Unprotected water 3) Pests 4) Untreated sewage 5) Infected animals 6) Improper Waste- management 7) soil , dust 63 31 Cross-contamination Contact hand contact surfaces food contact surfaces Dripping Dripping for example, juices or blood Transfer / being carried by people equipment other foods 64 Sources of physical and chemical contaminants • • • • • • • • • • • Physical People Packaging Raw food and the natural environment Buildings and equipment Pests Chemical Cleaning products Products used in agriculture Pest control products Metals 65 32 Sources of biological contaminants • Animals • Raw foods, such as – meat and poultry – Fish – eggs – vegetables • Water • Air and dust • People • Pests • Dirt, rubbish and waste food 66 Effects of Food contaminants • Short-term effect: – High dose – May be fatal • Long-term effect: – Low dose – Long-term damages: cancers and histological damages 67 33 Food Contamination and Spoilage Source of Contamination Criteria for judging whether food is fit for consumption Classification of food according to ease with which it spoils Conditions that could lead to food spoilage Signs of spoilage in fresh , dry and preserved foods. 68 Spoilage in foods begins as soon as: 1.Vegetables and fruits are harvested or picked 2.eggs are laid 3.fish is caught 4.an animal is slaughtered for meat 5.milk is drawn from the milk animal and continues till is consumed 69 34 • Food spoilage: decomposition or damage caused to food by various agents making it unsuitable for consumption. • Contaminated food: those foods which are not fit to be eaten for sanitary reasons ( although they may look, smell and taste good, they may contain harmful chemicals , non-food matter and bacteria. 70 • Spoilt food: those foods which look harmful and unfit to eat. It has an unattractive colour, smell, taste and appearance. 71 35 Classification of food spoilage Food spoilage can be classified into six groups: 1. Microbiological action 2. presence of contaminants 3. Action of insects 4. Natural enzymes: Signs of spoilage seen in fruits and vegetables include over maturing, softening, browning and sprouting. 5. physical changes: freezer burn, mechanical damage during harvesting and transporting foods, broken eggs can accelerate spoilage by microorganisms. 6.chemical reactions: chemical changes, which are not catalyzed by natural enzymes or action of micro- organisms such as reaction between acidic food and reform the can causes hydrogen swell in canned foods or oxidative rancidity, oxidative discoloration, flavor changes and nutritive loss. Spoiled food is best discarded. 72 Food Spoilage DECOMPOSITION / ROTTING / PERISHING / DECAYING. - Discolouration. - Visible mould. - Change in smell. - Change in texture. 73 36 Spoilage indicators in different categories of food • • • • • • Canned food: 1. cans have a puffy, swollen appearance 2. cans are leaky, corroded or rusty 3. contents spurt out when the can is opened 4.contents smell putrid or of hydrogen sulphide 5. brine or syrup looks cloudy, bubbly, slimy or moldy • 6.contents are discoloured 74 Common food vehicles for pathogens • • Pathogen Campylobacter jejuni or coli: Food sources Major: poultry. Minor: milk, mushrooms, clams, hamburger, water, cheese, pork, shellfish, eggs, cake icing. • Clostridium perfringens Major: meat, meat stews, meat pies, and beef, turkey, and chicken gravies. Minor: beans, seafood. • Escherichia coli O157:H7 Major: beef particularly ground beef. Minor: poultry, apple cider, raw milk, vegetables, cantaloupe, hot dogs, mayonnaise, salad bar items. 75 37 Common food vehicles for pathogens • Listeria monocytogenes – • Salmonella (non-typhoid) – • Major: poultry, meat, eggs, milk, and their products. Minor: vegetables, fruits, chocolate, peanuts, shellfish. Staphylococcus aureus – • Major: soft cheese, ground meat. Minor: poultry, dairy products, hot dogs, potato salad, chicken, seafood, vegetables. Major: workers handling foods: meat (especially sliced meat) poultry, fish, canned mushrooms. Minor: dairy products, prepared salad dressing, ham, salami, bakery items, custards, cheese. Vibrio sp. – Major: oysters. Minor: other seafood 76 77 38