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Controlling Micro-organisms

  • All foods change over time.
  • These changes are not always harmful e.g. hanging meat is more tender and blue cheese is created by moulds.
    Fodd eventauly becomes harmful or unpleasant to eatl; mmilk goes sour, fruit becomes mouldy and meat and fish can become putrid and can cause food poisoning.
  • To preserve food, i.e make it last longer and extend its shelf life, the ezymes and micro- organisms that cause these thing must be controlled.
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  • These are chemical catalysts that are found in all types of cells. They break down plant and animal tissues causing fruit to riper, meat to tenderize and oxidation to spped up. If enzyme activity is allowed to continue, there is food spoilage.
  • Oxidation takes place when fruit and vegetables are exposed to air after being cut. This causes the flesh to turn brown.
  • Adding acid - this is shown when adding lemon juice to fruit sald
  • Blanching- put carrots into bioloing water
  • Preventing contact with air- put peeled potatoes in cold water until needed.
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  • Single celled plants found in the air and on the skins of the fruit
  • Spoil the taste of food but dont make it harmful
  • Grow only on sugary foods
  • Cant survive without air
  • Cant grow at low temperatures
  • Cant survive in sugar concentration above 50 per cent.
  • cant survive in vingegar
  • are destyoed at temperatures above 70C
  • |to prevent yeasts growining you shouls store them at low temperatures. jams should be made with 60 per cent sugar in them
  • Yeast wwill ferment if in the right condiions which are  warmth, moisture, food and time.
  • Yeasts are used to make bread productts where the carbon dioxide is used as a rasing agent and alcholic drinks. Yeast can be fresh, dried or quick acting
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  • It is a type of fungus.
  • They settle on food and grow into a visible plant, which reselembles coloured fluff
  • grow on many foods, including bread, cheese and meat
  • like slighly acid conditions
  • need moisture
  • need warm temperatures between 20c-40c
  • destoryed at temperatures above 70C
  • can survive in a fridge, but not a freezer
  • If it is present it shows that the food is not that fresh or has been badly stored. Some moulds cause allergic reactions and respiratory problems.
  • Moulds are only used in manufacturing for blue cheese and also for quorn.
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