Preservation methods Flashcards
Canning
The food is packed into a metal can and heated until commercially sterile at 121 degrees centigrade. To create the seal special steamer used where vacuum is applied to draw air out and the vacuum continues until the lid is sealed in place the air is driven out by steam preventing bacteria survival.
UHT
UHT is a form of sterilisation used on milk. Firstly the milk is heated at 135 degrees centigrade for 1 second then it is added into a sterile container. This extends the shelf life due to the high temperature exposure most bacterium will be destroyed and as it is added into a sterile container this therefore means that no additional bacterium are added into the product therefore meaning that little to no bacteria will grow therefore increasing the shelf life.
Bottling
Toughened glass able to withstand high temperatures and that are easy to sterilise then the jars/bottles are filled with raw or cooked food and the food is heated slowly to boil foods destroying bacteria the air is expelled using a special lid and as the jar cools a vacuum is formed to seal it. This seal protects against re-entry of bacteria and due to no oxygen being able to enter or inside the product this prevents some bacteria multiplication. The process is commonly used on jams, pickles and chutney due to Glass is a non-reactive substance so suitable for acidic mixtures. Bottled food have a very long shelf life at ambient temperatures.
