LO: To understand how to answer exam questions on Food Preservation and Spoilage Must: Take part in the group discussions and contribute to the answers given. Should: Be able to structure an extended answer, (be able to complete questions starting with ‘explain’, ‘summarise’ or ‘discuss’). Could: Motivate and inspire others by taking a leading role within your group. Food Preservation • Food is preserved to extend the shelf life of a product (make it last longer) and to stop it from spoiling (going off). Food spoilage can be caused by, natural decay, contamination by microorganisms and action of enzymes. Micro-organisms come in 3 groups: • Yeasts - active in warm, moist conditions. Found in the air, soil & skin of fruit. Able to break down sugars to produce Alcohol and carbon dioxide. This is known as fermentation and helps when making bread, alcoholic drinks and yeast extract spreads (marmite, vegemite). • Moulds - fungi that grow in food. Black, white or blue in colour. Prefer moist/humid conditions. Can be harmful but can also be used to produce special types of cheese. • Bacteria - most active (reproduce rapidly) in optimum temperature of 37 degrees. It is the pathogenic, (bad), bacteria that will cause food poisoning or food-borne illnesses, resulting in serious illness or even death. Toxins are the poison that a bacteria produces that cause illness. There are 6 things that affect the growth of micro-organisms: • Time • Temperature • Food • pH • Oxygen • Moisture MAP – Modified Atmosphere Packaging • Most of the oxygen is removed from the packet. • This works because most bacteria need oxygen to reproduce • Sometimes a vacuum is used (vacuum packing) • Sometimes the oxygen is replaced with another gas e.g. Nitrogen or Carbon Dioxide. This also alters the pH of the food. • Examples are salad, bacon, and smoked fish Chilling / Refrigerating • This keeps food fresh for short periods of time. • Chilled food is stored between 1°C and 8°C. • The best temperature is below 4°C as this will stop Listeria reproducing. • Chilled meals must be re-heated to 72°C and eaten within 2 hours or thrown away. They must not be re-heated more than once. • Chilling foods slows down bacteria growth and enzyme activity. This speeds up again in warmer temperatures. Freezing • This keeps food fresh for longer periods of time. • Frozen food is stored between -18°C and -29°C. • There is a high demand for frozen food because it is very convenient and can last between 3 and 18 months. • Freezing food causes bacteria to become dormant ,(go to sleep). As food is thawed (defrosted) the bacteria start to reproduce again. • Some people avoid frozen food because they think it loses taste and nutritional value. • Freezer burn can affect frozen food that has been stored for a very long time or is badly packed. The food becomes very dry and can have white spots or marks on it. Canning • Canning is a way of sterilising food to make it last a very long time (years). • Food is either sealed in cans and then sterilised, or sterilised and packed into sterile (germ free) containers. • The time and temperatures used depend on the food. Baked Beans are heated to 120°C for 33 minutes and then rapidly cooled. • Once a can is opened spare food may be saved in the fridge for a couple of days. However, it should be put in a clean container or dish and never stored in the can itself. What is a high risk food? Egg Products Gravies and Soups Raw or cooked meat and poultry Raw or cooked fish Food poisoning bacteria can grow and multiply on some types of food more easily than others. High risk foods are moist and rich in protein, they include: Shellfish Cooked Rice and lentils Prepared salads The Danger Zone The core (middle) temperature of high risk foods should be 72 °C for at least 2 minutes Most bacteria multiply above 5 °and below 63 °C. Any temperature in this range is in the danger zone. High-risk foods are stored below 5 °C and cooked above 63 °C and cooked to a core temperature of 72 °C degrees for at least two minutes. Frozen foods should be kept below -18°C Cross Contamination This happens when food handlers transfer bacteria from one food to another. It can cause food poisoning and happens when: Bacteria are carried on equipment e.g. hands, dirty cloths, knives and chopping boards Liquid or juices drip from raw food onto a high risk food Raw food touches high risk food Coloured Chopping Boards and Equipment • Using colour coded equipment for different food helps to prevent cross contamination. Some Pathogens (bad micro-organisms) Pathogen Where found Clostridium Botulinum (Botulism) Seafood, Canned food, meat, sausages. Listeria Soft cheese, pate, poorly stored /re-heated ready meals, unpasteurised milk Salmonella Eggs and Poultry E-coli Raw Meat Staph A Food handlers noses, mouths, hands and in septic cuts Bacillus Cereus Rice, lentils and beans HACCP HAZARD ANALYSIS CRITICAL CONTROL POINTS A system to make sure food is produced and stored safely. Like the Hazard Chart you produced in your coursework. A CCP is a Critical Control Point for example specified cooking time and temperature. It is a check put in place at important processing points to ensure that food is safe to eat. Types of Contamination Physical Chemical Microbiological Hair Bleach Yeasts Metal Detergent Moulds Wood Washing Up Liquid Bacteria Plastic Any cleaning material Rubber Pesticides Teeth and Bones LO Review: To understand how to answer exam questions on Food Preservation and Spoilage Must: Take part in the group discussions and contribute to the answers given. Should: Be able to structure an extended answer, (be able to complete questions starting with ‘explain’, ‘summarise’ or ‘discuss’). Could: Motivate and inspire others by taking a leading role within your group.
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