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Food Spoilage and Food Poisoning Food Spoilage Natural Decay Contaminated by microscopic forms of life (micro-organisms) Perishable Foods Foods spoil rapidly due to: Large amounts of water and nutrients Examples include: • milk • fruit • Meat Natural Decay Moisture Loss • When water in the vegetable is not replaced • Vegetable or fruit shrinks and becomes limp • Skin becomes wrinkled and leathery Natural Decay Action of enzymes Enzymes speed up the process of decay by breaking down the foods tissues components creating: • Oxidation – destruction of certain nutrients by enzymes in food reacting with the air • Browning – If apples are cut or bruised they will discolour • Ripening - Enzymes involved in ripening of fruit (Banana Green – yellow - Brown) Contamination by micro-organisms The main micro-organisms are: • Yeast • Bacteria • Moulds Food is an ideal medium for micro-organisms as it provides: • nutrients –vitamins! • moisture – water ! This helps the bacteria to survive Friendly Bacteria • Not all bacteria are harmful! • Some are used in the food industry to produce: • Yoghurt • Cheese • Soy sauce Food Poisoning Bacteria Bacteria are the most common form of food Poisoning. Symptoms include: • Vomiting • Diarrhoea • Stomach cramps What do bacteria need to survive?! • Food • Warmth • Moisture • Time How does warmth effect the growth of bacteria • see Boardworks presentation KS4 Moisture Bacteria need moisture to grow: • Dried foods have a long shelf life as they do not contain water. In foods with • high levels of sugar - jams • High levels of salt - salami • High levels of acid - pickles Water is not available in the food to grow due to high levels of salt sugar and vinegar Foods that bacteria like Bacteria prefer foods that are high in PROTEIN: These are known as HIGH RISK FOODS High risk foods include: • Meat and poultry • Eggs • Fish • Mayonnaise • Dairy products Bacteria multiplication • Bacteria can multiply by splitting every 10-20 minutes • In just 45 minutes one bacterium will have multiplied to 1 million bacteria Dangers of Food Poisoning • Cross contamination • Blood juices from raw food dripping onto cooked food • Bacteria being transferred from one food to another on hands tools and equipment