There are a number of methods of preservation, the chosen one just depends on cost, commercial use and type of product.

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  • There are a number of methods of preservation, the chosen one just depends on cost, commercial use and type of product.
    • Heat methods
      • canning
        • Heat kills bacteria and enzymes
        • Can cause changes in colour and texture. Loss of Vitamin C.
        • Lasts many years
        • Used for fish, meat, fruit, eggs and milk
      • bottling
        • Heat kills bacteria and enzymes
        • lasts for many years
        • can cause change in colour or texture. Loss of vitamin C.
        • Used for fruit and veg
      • pasteurization
        • Most bacteria killed at 72 degrees
        • Little effect on flavour
        • Not all bacteria killed
        • Used on milk, cream and orange juice.
      • ultra heat treatment
        • All bacteria killed at 132 degrees.
        • Lasts for several months
        • changes taste slightly
        • used for milk and fruit juices.
      • sterilisation
        • Food heated to 104 degrees for 40 minutes
        • Extends life of milk to bout 10 days.
        • gives a creamy flavour and colour
        • used on milk and fruit juices.
    • Low temp methods
      • Freezing
        • stops bacteria and enzyme activity. Domestic freezers at -18 degrees or below
        • Can be frozen for many months with little lose of vitamins
        • Slow freezing breaks down cells and changes texture
        • Used for ready meals, fruit, veg, ice-cream, meat and fish
      • Chilling
        • slows bacteria growth- domestic fridges at 4 degrees or below
        • Good colour and flavour kept
        • Short storage life
        • used for ready prepared meals e.g lasagne
    • Removing moisture methods
      • Drying
        • removal of moisture stops bacteria growth
        • lasta for long periods of time
        • most vitamin c lost and must be kept dry
        • used for soups, pasta, beans and packet desserts
      • Acclerated freeze drying
        • food frozen than quickly dried
        • good colour and flavour
        • can be expensive
        • Used on coffee
    • Chemical methods
      • pickling
        • increases acidity of foods
        • long shelf life
        • very strong flavour
        • used for onions, cabbage and olives
      • Salting
        • reduces water content by osmosis
        • long shelf life
        • product needs to be soakedbefore cooking
        • used for meat, fish and green beans
      • smoking
        • slow method which prevents bacterial growth
        • adds flavour
        • kills vitamin b and c
        • used for bacon, cheese and fish
      • sugar
        • over 60% stops micro-organisem growth
        • long shelf life
        • high jam temps kill vitamin c
        • jams, marmalades and crystallised fruits
    • Atmosphere control
      • vacuum packing
        • removes all oxygen
        • retains vitamins
        • often still needs refiridgearating
        • Used for bacon and fish
      • modified atmosphere packaging
        • replaces with oxygen with nitrogen and CO2
        • Colour and flavour are good
        • Expensive
        • Used for meat, salads, minced beef and bacon

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