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neurologyYou need to know

• Food spoilage is the loss of food quality that makes food inedible.
• Food spoilage can result from the growth of microorganisms or from enzyme activity within food.
• Microorganisms are microscopic living organisms.
• Bacteria, yeasts and moulds are microorganisms.
• Some microorganisms spoil food, and some pathogenic bacteria can cause food poisoning.
• Microorganisms need warmth, moisture, nutrients, a suitable pH and enough time to multiply to harmful levels.
• Most microorganisms grow best in warm conditions, while chilling and freezing slow their growth.
• High temperatures during cooking destroy many microorganisms and reduce the risk of food poisoning.
• Most microorganisms do not grow well in highly acidic or highly alkaline conditions.
• Pickling preserves food by lowering pH and creating acidic conditions that inhibit microorganism growth.
• Drying, salting and adding large amounts of sugar preserve food by reducing water availability for microorganisms.
• Leaving food at room temperature for longer gives microorganisms more time to multiply.
• High risk foods are ready-to-eat foods that are moist, usually high in protein, and easily support the growth of pathogenic bacteria.
• High risk foods are especially hazardous because they are eaten without further cooking that could destroy pathogenic bacteria.
• Cooked meat, fish, dairy products, some egg products, precooked shellfish, gravies, stocks, sauces and cooked rice are common high risk foods.
• Enzymes are biological catalysts, and most food enzymes are proteins.
• Enzymes speed up chemical reactions in food and can therefore cause spoilage.
• Enzymic browning happens when enzymes in cut fruit or vegetables catalyse reactions that turn the exposed surface brown.
• Heating food denatures enzymes by changing their structure, so the enzymes can no longer catalyse spoilage reactions.
• Vegetables are often blanched briefly in boiling water before freezing because freezing does not destroy enzymes, but blanching denatures them and slows spoilage during storage.
• Acidic ingredients such as lemon juice reduce enzyme activity and slow enzymic browning in cut fruit.
• Food spoilage can be caused by enzymes and by microorganisms such as moulds, yeasts and bacteria.
• Enzymic browning occurs when enzymes in cut fruit react with oxygen in the air and turn the exposed surface brown.
• Apples and pears commonly show enzymic browning soon after they are sliced.
• Enzyme activity can make fruits such as bananas and avocados become overripe.
• Overripe bananas become brown and soft because of enzyme action.
• Moulds are fungi that spread by growing thread-like filaments.
• Moulds can grow on food in acidic or alkaline conditions, in foods with high sugar or high salt, in moist or fairly dry conditions, and in warm temperatures.
• Bread, cheese, jam and fruit are common foods on which moulds grow.
• Mould spoilage often appears as furry white, green or black patches on food.
• Visible mould on the surface of food shows that microscopic mould has also spread within the food.
• Yeasts are single-celled fungi.
• Yeasts can grow with or without oxygen when there is enough warmth and moisture.
• Yeasts often spoil acidic, sweet foods such as grapes, strawberries, tomatoes, fruit juice, honey, jam and sweetened yoghurt.
• In the absence of oxygen, yeasts ferment sugars in food to produce alcohol and carbon dioxide.
• Carbon dioxide gas bubbles on the surface of a liquid can be a sign of yeast spoilage.
• An alcoholic taste can be a sign that yeasts have spoiled a food.
• A slightly fizzy mouthfeel can be a sign that yeasts have spoiled a food.
• Some microorganisms are intentionally used in food production even though other microorganisms cause food spoilage.
• Blue cheeses such as Stilton, Gorgonzola and Roquefort are made using specific edible moulds.
• In blue cheese production, selected moulds create blue-green veins, a creamy texture and a sharp tangy flavour.
• The moulds used in blue cheese are chosen because they are safe to eat, unlike some other moulds.
• Yeast is used as a raising agent in bread making.
• In bread making, kneading helps to distribute yeast evenly through the dough and develop gluten.
• Sugar may be added to bread dough to provide the yeast with an easily available fuel source.
• During bread making, yeast respires using sugars in the dough and produces carbon dioxide gas.
• Carbon dioxide becomes trapped in the gluten network as bubbles, which makes bread dough rise during proving.
• Proving is the stage in bread making when dough is kept warm so yeast can produce enough carbon dioxide to raise it.
• During baking, the carbon dioxide bubbles expand and cause the bread to rise further.
• Baking kills the yeast in bread dough.
• In yoghurt production, milk is first heat-treated to kill harmful or unwanted bacteria before a starter culture is added.
• A starter culture is a selected population of useful bacteria added to milk to begin yoghurt production.
• During yoghurt production, the milk is kept warm so bacteria can ferment lactose and produce lactic acid.
• In yoghurt production, lactic acid denatures milk proteins and causes coagulation, which thickens the milk into yoghurt.
• Lactic acid gives yoghurt its sour flavour.
• Cheese production also uses bacteria to acidify and thicken the milk before rennet is added.
• Rennet is an enzyme that separates milk into solid curds and liquid whey.
• In cheese making, the curds are heated, pressed and salted after the whey is removed.
• Salt helps to flavour cheese and preserve it by reducing spoilage.
• Some cheeses are matured after processing to develop their final texture and flavour.
• The bacteria used in yoghurt and cheese making are selected because they produce the desired changes in milk without being harmful.
• Contamination by harmful bacteria can spoil milk and make yoghurt or cheese unsafe to eat.
• Food poisoning is illness caused by eating food contaminated with harmful bacteria and commonly causes nausea, vomiting, diarrhoea, stomach pain, and fever.
• Serious food poisoning can be fatal, especially for the very young, elderly people, pregnant women, and people with weakened immune systems.
• Cross-contamination is the transfer of harmful bacteria from contaminated food, surfaces, equipment, people, pests, or waste to other food.
• Raw meat, poultry, eggs, seafood, and vegetables contaminated with soil are common sources of bacterial contamination.
• Harmful bacteria can spread when raw food touches cooked or ready-to-eat food during storage or preparation.
• Raw food should be stored separately from cooked or ready-to-eat food to prevent cross-contamination.
• Defrosting raw food should be kept at the bottom of the fridge so that drips cannot contaminate other food.
• Raw vegetables and salad ingredients should be washed thoroughly to remove soil and harmful bacteria.
• Unclean work surfaces, utensils, chopping boards, and cloths can transfer bacteria to food.
• Work surfaces and equipment should be cleaned thoroughly with hot soapy water or a suitable antibacterial cleaner after use.
• Separate chopping boards and utensils should be used for raw and ready-to-eat foods.
• Clean cloths or disposable paper towels should be used because dirty cloths can spread bacteria around a kitchen.
• Food handlers can contaminate food through unwashed hands, coughing, sneezing, touching the face or hair, or handling food when ill.
• Hands should be washed before preparing food, after handling raw food, after touching the face or hair, and after using the toilet.
• Cuts should be covered with waterproof dressings and long hair should be tied back or covered to reduce contamination from food handlers.
• A clean spoon should be used each time food is tasted so that bacteria are not transferred back into food.
• Cooking utensils should be held by the handles to avoid contaminating the parts that touch food.
• Pests such as flies, cockroaches, and rodents can contaminate food with bacteria from their bodies, urine, and faeces.
• Keeping doors and windows closed or screened and covering food helps stop pests contaminating food preparation areas.
• Waste food and rubbish are sources of bacterial contamination and should be kept in lidded, preferably foot-operated bins.
• Bins should be emptied regularly and before they overflow to reduce bacterial contamination and pest activity.
• Harmful bacteria multiply quickly in warm conditions, so food should not be left out at room temperature longer than necessary.
• Food should be covered while it cools to reduce contamination from pests and accidental contact.
• Food should be cooked thoroughly to a high enough temperature to kill most harmful bacteria.
• Food should be served immediately after cooking or chilled quickly in a fridge or freezer to slow bacterial growth.
• Pasteurisation kills harmful bacteria in milk by heating the milk before it is sold.
• Campylobacter is commonly found in raw poultry, raw meat, unpasteurised milk, and untreated water.
• Campylobacter risk is reduced by preventing cross-contamination from raw poultry and cooking poultry thoroughly.
• Escherichia coli is commonly found in raw minced beef, unpasteurised milk, untreated water, and contaminated salad vegetables.
• Escherichia coli risk is reduced by cooking minced beef thoroughly, washing vegetables, and avoiding unpasteurised milk.
• Salmonella is commonly found in raw poultry, eggs, and unpasteurised milk.
• Salmonella risk is reduced by thorough cooking, careful egg handling, good kitchen hygiene, and vaccinating poultry flocks.
• Listeria is commonly found in unpasteurised milk, soft cheeses, pate, and chilled ready-to-eat foods.
• Listeria risk is reduced by refrigeration, following use-by dates, and avoiding high-risk foods during pregnancy.
• Staphylococcus aureus is commonly carried on human skin, in the nose, and on hair.
• Staphylococcus aureus contamination is reduced by good personal hygiene, covering cuts, and keeping ill food handlers away from food.
• People at greater risk of food poisoning should avoid high-risk foods such as unpasteurised dairy products and undercooked meat or eggs.
• Correct food storage after buying and before eating reduces spoilage and helps keep food safe to eat.
• Storing food at the correct temperature slows spoilage because microorganisms such as bacteria grow and reproduce more slowly.
• Freezing food at about -18°C makes microorganisms dormant and stops their growth, so frozen food keeps for much longer.
• Chilling food at 0°C to below 5°C slows the growth of microorganisms and extends shelf life.
• The temperature danger zone is 5°C to 63°C because microorganisms can grow and reproduce within this range.
• Cooking food to 75°C kills harmful microorganisms, and reheated food should also reach 75°C.
• A temperature probe can be used to check that the centre of food has reached 75°C during cooking or reheating.
• Perishable foods such as meat, fish, dairy products, and many fruits and vegetables have a short shelf life because microorganisms grow easily in them.
• Perishable food should be kept below 5°C or above 63°C whenever possible.
• Food should not be reheated more than once because each cooling and reheating cycle increases the time spent in the temperature danger zone.
• Ambient storage means storing food at room temperature, which is generally about 17°C to 20°C.
• Non-perishable foods can be stored at ambient temperature because processing or packaging prevents or slows the growth of microorganisms.
• Drying preserves food by removing water, so microorganisms do not have enough moisture to grow.
• Tinning preserves food by heating it to kill microorganisms and then sealing the container to prevent contamination.
• Vacuum packing preserves food by removing air from the packaging, which reduces the growth of many spoilage microorganisms.
• Pickling preserves food because the low pH of vinegar prevents the growth of many microorganisms.
• In the UK, eggs can be stored at ambient temperature because hens are vaccinated against salmonella.
• A domestic fridge should be kept between 0°C and 5°C.
• Food in a fridge should be wrapped, covered, or stored in separate containers to reduce the risk of cross-contamination.
• Hot food should be allowed to cool before it is put into a fridge so that it does not raise the fridge temperature.
• Raw meat and defrosting meat should be stored at the bottom of the fridge so that drips cannot contaminate ready-to-eat food.
• A domestic freezer should be kept at about -18°C.
• Frozen food should be labelled with the date it was frozen so that it is not kept for too long.
• A freezer should not be overfilled because cold air must circulate between items.
• Food stored in a freezer should be wrapped well to prevent freezer burn and loss of quality.
• Frozen food should be defrosted in the fridge so that it stays out of the temperature danger zone as much as possible.
• Defrosted food should not be refrozen because microorganisms can begin growing again as the food warms.
• Food producers use date marks because food will eventually spoil even when it has been stored correctly.
• A best before date refers to food quality rather than food safety, so food may still be safe after this date even though quality has declined.
• A use by date is used mainly on foods with a short shelf life and relates to food safety.
• Eating food after its use by date increases the risk of food poisoning.
• Food should be covered whenever it is stored before cooking or left after preparation and before serving.
• Covering food helps prevent it from drying out.
• Covering food helps stop pests, dust, and dirt from contaminating it.
• Food safety during preparation, cooking and serving depends on preventing contamination and controlling the conditions in which microorganisms multiply.
• Good personal hygiene reduces the transfer of harmful microorganisms from the food handler to food.
• Hands must be washed thoroughly with hot water and soap before handling food and after using the toilet, touching the face, handling waste or eating.
• Food handlers should avoid coughing or sneezing over food because droplets can contaminate food with microorganisms.
• Clean protective clothing and covered hair reduce the risk of bacterial and physical contamination of food.
• Cuts should be covered with a blue waterproof plaster so that the dressing is visible if it falls into food.
• People who are ill, especially with sickness or diarrhoea, should not prepare food because they may spread pathogens.
• Work surfaces, chopping boards and utensils must be cleaned before and after use to prevent microorganisms transferring to food.
• Hot soapy water removes grease and food residues, and antibacterial cleaners reduce the number of bacteria on work surfaces.
• Raw food must be kept separate from cooked and ready-to-eat food during storage, preparation and serving to prevent cross-contamination.
• Separate utensils should be used for raw and cooked foods so that microorganisms from raw food are not transferred to food that will not be cooked again.
• In the standard colour-coding system, red chopping boards are used for raw meat, blue for raw fish, yellow for cooked meat, green for fruit and vegetables, and white for dairy products.
• Knife skills must be used hygienically, so knives used on raw meat, fish or high-risk foods must be cleaned and sanitised before being used on ready-to-eat ingredients.
• Fruit and vegetables should be washed thoroughly before preparation to remove soil and reduce surface contamination.
• Food must be cooked for long enough and at a high enough temperature to destroy harmful microorganisms throughout the food.
• Cooking times vary with the size, thickness and type of food, so larger or thicker portions need longer heating.
• Different foods have different safe cooking requirements, so the target time and temperature must match the food being prepared.
• A temperature probe checks the internal temperature of food and should be inserted into the thickest part to give the most reliable reading.
• A food temperature probe must be cleaned and sanitised before and after use to avoid contaminating food.
• A core temperature of 75 °C is a standard food-safety check for many thoroughly cooked and reheated foods.
• A clean knife or skewer can be inserted into the thickest part of food to check texture and whether the centre is cooked.
• Finger tests, taste tests, visual checks and sound checks can help judge readiness, but they are less reliable than a cleaned temperature probe for high-risk foods.
• Food that is still partly frozen may not cook safely because the centre can remain below a safe temperature.
• Frozen food should be defrosted fully in a refrigerator rather than at room temperature because chilled conditions slow microorganism growth.
• Food being defrosted should be kept on the bottom shelf of the fridge or in a covered container so that drips cannot contaminate other foods.
• Reheated food must be heated thoroughly and evenly so that the centre reaches a safe temperature.
• Food should not be reheated more than once because repeated cooling and reheating increase the time spent in temperatures where microorganisms multiply quickly.
• High-risk foods are foods that provide favourable conditions for microorganism growth and are more likely to cause food poisoning if handled badly.
• High-risk foods are often moist, high in protein and ready to eat without further cooking.
• Examples of high-risk foods include cooked meat and fish, dairy products, cooked rice, egg products and cooked shellfish.
• High-risk foods must be stored, prepared and served carefully because they may not receive any further heating to destroy microorganisms.
• High-risk foods should be kept separate from raw foods and from equipment used for raw foods to reduce cross-contamination.
• Wet mixtures such as falafels, fish cakes and meatballs require careful hygienic handling because contamination can be mixed throughout the product.
• High-risk wet mixtures should be shaped with clean hands or utensils and then cooked thoroughly to a safe internal temperature.
• A blender can be used hygienically to make fruit coulis only if the fruit has been washed and dried and the blender has been cleaned before use.
• Cooked food must be served with clean utensils and on clean plates so that it is not recontaminated after cooking.

• Analyse how temperature, moisture, pH, food supply and time affect microorganism growth in a given food safety scenario.
• Explain why a named food is high risk by referring to moisture, protein content, readiness to eat and likelihood of further heating.
• Interpret signs of spoilage in fruit, bread, cheese or liquids to identify whether enzyme action, mould growth or yeast action is the most likely cause.
• Explain how blanching, chilling, freezing, drying, salting, sugaring or pickling control spoilage by changing conditions for enzymes or microorganisms.
• Compare chilling, freezing and ambient storage to justify the safest storage method for a named food.
• Select suitable storage locations in a fridge or freezer to keep raw, defrosting and ready-to-eat foods separate.
• Interpret best before and use by dates to decide whether a food quality issue or a food safety issue is involved.
• Plan safe cooling, covering and storage steps for cooked food so it spends as little time as possible in the danger zone.
• Carry out hygienic handwashing and personal hygiene routines at the correct points during food preparation.
• Select and sanitise suitable work surfaces, cloths, chopping boards and utensils for raw and ready-to-eat foods.
• Explain how cross-contamination can occur from food, equipment, handlers, pests or waste in a named preparation task.
• Carry out safe defrosting of frozen food in a refrigerator and position it to prevent drips contaminating other foods.
• Use a cleaned temperature probe correctly by inserting it into the thickest part of food and interpreting whether 75°C has been reached.
• Evaluate whether a food has cooked safely by combining probe evidence with appropriate visual or texture checks.
• Plan safe reheating of cooked food and justify why it should not be reheated more than once.
• Explain how yeast functions in bread making from kneading and proving through to gas expansion in baking.
• Explain how bacteria and rennet are used to produce yoghurt or cheese and why starter cultures must be controlled.
• Compare harmful bacterial contamination with the controlled use of microorganisms in bread, yoghurt, cheese and blue cheese production.
• Justify control measures for named food poisoning bacteria by linking each organism to its common source and prevention method.