food preservation Flashcards
Preservation of food
Used for: Surplus food can be stored and used in time of shortage Enjoy seasonal fruit all year round Enable food to be transported long distances without spoilage/decay Allow foods to be stored for a long time at home without going off 6 methods 1. high temperature
2. low temperature
3. chemical
4. removing moisture
5. controlling the atmosphere
6. irradiation
Canning
High temperature Heating can to 120°C for 10 minutes to sterilise the contents and kill spores Food added to can before being filled with liquid and sealed under a vacuum Does alter flavour e.g. peaches
Pasteurisation
High temperature Rapidly heating liquid to 72°C for 15 seconds, then rapidly cooled to 10°C Kills bacteria e.g. milk
Bottling
High temperature Fruit/veg in glass bottles, water/liquid added, heated in oven, lid on for air tight seal
e.g. seasonal fruit and veg
UHT
High temperature 130-150°C for 1-3 seconds Nearly all microorganisms/enzymes are killed Little change to flavour/colour of food e.g. milk
Sterilisation
High temperature Heated to 104°C for 40 minutes/130°C for 15 minutes Nearly all microorganisms/enzymes are killed Does change flavour e.g. milk
Freezing
Low temperature Storing foods at -18°C Short term method, star system used Key: 1 week **1 month **18 weeks Types · Plate freezing – flat products are frozen between two plates e.g. burgers · blast freezing – freezing air blasted over irregular shaped foods e.g. fruit and veg · cryogenic/immersion freezing – food immersed/sprayed with liquid nitrogen expensive, used with delicate foods e.g. raspberries
Modified atmosphere
packaging (MAP)
Controlling temperature Atmosphere inside packaging maintains colour of dish and delays spoilage, gases are used to control this have been put into packaging e.g. ready meals
Vacuum packing
Controlling temperature Tight air seal on packaging to there is no oxygen, bacteria can’t grow Can make food quite tough when cooked e.g. meat
