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Food Spoilage. Food has a limited life. After a certain time it will go off or spoil. Food spoilage is caused by: chemicals found in food called enzymes ; by air; or by micro-organisms, e.g. moulds, yeast and bacteria (which are also called germs).
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Food Spoilage • Food has a limited life. After a certain time it will go off or spoil. • Food spoilage is caused by: chemicals found in food called enzymes; by air; or by micro-organisms, e.g. moulds, yeast and bacteria (which are also called germs). • Food spoilage occurs more quickly when food is: • not stored correctly • prepared in a dirty kitchen • handled by a person who is careless or unhygienic
Enzymes • Chemicals that are naturally present in fruit and vegetables. • They help food to ripen. • After food has been harvested, enzymes continue to ripen it, eventually causing it to becoming over-ripe and decay.
Micro-organisms • Micro-organisms are tiny living organisms called germs. They include bacteria, yeasts and moulds. • They are all around us: in soil, air, water, in humans and animals. • Most micro-organisms are harmless in small amounts, but in large amounts they can cause food poisoning. Examples include bacteria, yeasts and moulds.
Micro-organisms: Moulds In certain conditions, moulds form a furry growth on fruit and bread.
Micro-organisms: Yeasts Yeasts cause fruit and jam to go off.
Micro-organisms: Bacteria Bacteria cause food poisoning, as well as causing animal foods like meat and fish to spoil.
Food Spoilage: Oxygen • Oxygen in the air causes fats to go off or become rancid. This is why unwrapped items like butter develop ‘off’ flavours. • Oxygen also reacts with enzymes, causing discolouration of foods, e.g. apples go brown.
Food Poisoning • Food poisoning occurs when a person eats or drinks foods that have large numbers of pathogenic (disease causing) bacteria. When they enter our body they multiply very quickly and make us sick. • Often foods show no signs of spoilage because there is no change in colour taste or smell.
Symptoms of Food Poisoning Symptoms include: • Nausea • Vomiting • Abdominal pains • Cramps • Diarrhoea • High temperature
Food Poisoning Bacteria: Salmonella • Found everywhere, but especially in the intestines of humans, birds and animals. • Poultry, eggs and raw meat are sources of salmonella food poisoning. • Pets, rats, mice and insects carry salmonella and spread it to our food. • It can also be spread as a result of carelessness in personal hygiene in the bathroom and kitchen, e.g. not washing hands after going to the toilet.
Food Poisoning Bacteria: Staphylococci • Found mainly in humans – in the nose, mouth, throat and in cuts and boils. • Passed from humans to food during food preparation, e.g. sneezing or coughing over food, or through uncovered cuts.
Food Poisoning Bacteria: Listeria • Multiply at a lower temperature than most bacteria, e.g. in a fridge so can be in soft cheese, mayonnaises and pâté. • Present in soil on unwashed fruit, vegetables and salads. • Heathy adults are not usually affected by listeria but they can cause food poisoning and serious side effects in babies, older people and pregnant women.
Food Poisoning Bacteria: Clostridium Botulinum • Botulism is an extremely rare but very serious type of food poisoning. • It can result in paralysis and even death. • Clostridium Botulinum multiplies in faulty cans of food so always examine cans before buying – they must not be rusted, leaking or bulging.
Food Poisoning Bacteria: E. coli • E. coli lives in the intestines of cattle and sheep and can pass into the food chain through the faeces of these animals. • E. coli can also contaminate water supplies.
Food Poisoning Bacteria: Campylobacter • Found in raw poultry and meat, unpasteurised milk and untreated water. • Pets with diarrhoea can also be a source of infection. • It is the most common type of food poisoning in Ireland.
Food Hygiene • Bacteria are tiny invisible (to the human eye) living cells, which are found everywhere: in the air, water, soil, animals and humans. • In small amounts they do little harm – this is known as an acceptable level of contamination. • However, in larger amounts,they are dangerous.In the right conditions, they multiply rapidily, causing disease and sometimes death.
Food Hygiene: Conditions for Growth of Micro-organisms Warmth • Most micro-organisms grow best at 30–40⁰C so a warm kitchen is a suitable place for bacterial growth. • Our body temperature is 37⁰C so bacteria multiply in the human body and make us sick. • Low temperatures, such as in a fridge (4⁰C), slow down the growth, and very low temperatures like freezing inactivates them (0⁰C or lower) but does not kill them. • High temperatures used in cooking kill them. • Disinfectants also kill bacteria.
Food Hygiene: Conditions for Growth of Micro-organisms (continued) Moisture • All micro-organisms need moisture to grow and multiply. A lot of moisture is created in a kitchen during cooking and washing-up. Damp surfaces allow micro-organisms to thrive. • Most foods contains moisture, so bacteria can grow on these. • Bacteria do not grow on dried foods such as flour.
Food Hygiene: Conditions for Growth of Micro-organisms (continued) Food • All micro-organisms need food to survive. They feed on food, dirt and dust, so they grow well in a kitchen. • They grow and multiply quickly in protein foods like raw meat, fish and poultry, and in liquid foods like milk and custard. A lot of care needs to be taken when storing, preparing and cooking these foods.
Food Hygiene: Conditions for Growth of Micro-organisms (continued) Oxygen • Micro-organisms need air to grow and multiply, so food should be tightly wrapped to exclude air. • Some can survive without air, e.g. in canned or bottled foods. Time • Micro-organisms multiply quickly, so store food correctly and use it while it is fresh. • A single micro-organism becomes two micro-organisms every 20 minutes.
Tips to Prevent Food Poisoning • To avoid food contamination and food poisoning, food should be kept: • In cool dry storage areas, e.g. the fridge • Clean and covered • In a well-ventilated kitchen to remove moisture
How Does Food Become Infected with Bacteria? • Careless and unhygienic food handlers Not washing hands, especially after using the toilet, not covering cuts, or coughing and sneezing over food can all lead to infected food. • Dirt and grease Dirty preparation areas, equipment, utensils and kitchen cloths all provide food for bacteria to multiply.
How Does Food Become Infected with Bacteria? (continued) • Bacteriaare carried and transferred to food by: • Household pets, e.g. dogs and cats • Insects like flies and cockroaches • Vermin, e.g. mice and rats
How Does Food Become Infected with Bacteria? (continued) • Cross-contamination Thisis the transfer of bacteria from raw to cooked food from a food handler, or from dirty equipment or surfaces, e.g. if raw chicken is prepared on the same surface as salad, bacteria can cross from the raw chicken to the salad, which can result in food poisoning. To reduce the risk of cross-contamination, food premises use coloured-coded equipment, e.g. chopping boards and knives.
Case Study Activity Read Case Study 7.4 and answer the questions that follow. • Think–Pair–Share Activity • Compile a set of guidelines for: • a) Food handlers • b) Preparing food • c) Kitchen hygiene See Activity 7.4 in the TRB
Kitchen Hygiene and Safety:Quick Quiz • What is meant by food spoilage? • What causes food to spoil? • Outline the conditions needed for bacteria to grow. • State the causes of food poisoning. • List the symptoms of food poisoning.
