Processing Techniques Flashcards
food preservation
Food preservation is the prevention of bacterial and fungal growth that causes food to decompose or deteriorate.
One major reason is to preserve food in order to be able to eat it in the future.
types of processing techniques used to preserve foods
temperature - heat/cold
exposure to air
pH level
addition of chemicals - salt/sugar
removal of moisture
manipulation
heat
Food becomes ‘preserved’ when they are heated to 100°C.
Common methods of applying heat to preserve food is the canning and bottling processes.
Even the act of cooking food to 100°C will help preserve food for a period of time as the bacteria has been killed, To keep it safe, it then needs to either stay above 60°C or kept cold(below 5°C).
cold
The process of applying cold temperatures to food such as freezing or refrigerating is a good method for preserving food as it is simple.
It is important to have the appropriate containers to freeze items, they should be kept airtight.
Cook-Freeze – It is important to cool foods to not steaming before placing in the freezer.
Cook-Chill – Food needs to be chilled within 30 minutes of cooking and refrigerated between 0 and 3°C. It is then food for 5 days but must be reheated to at least 70°C before eating.
exposure to air
Dehydration and drying are techniques used to preserve food by either using the sun or an oven on a low temperature.
Drying refers to the removal of moisture where dehydration involves drying a food that can then be reconstituted back into its original state.
Traditionally foods that were dried included meat, eggs, fish and rice.
Nowadays, many foods are dried and dehydrated including food for people out trekking use.
To dry food, it is prepared, marinated and maybe blanched then placed on a rack in a 60°C oven for a number of hours.
acid
One way to store food is to reduce the pH and that is by adding an acid such as vinegar, lemon juice or citric acid.
Foods suitable for this method include onion, capsicum, cucumber, cauliflower, peas, carrots, beans, olive and fish.
Pickling foods generally last up to 3 months.
alkali
Adding an Alkali such as bicarbonate soda does not work as a preservation technique but it does counterbalance and neutralises acids.
An example of neutralising is when baking a sourdough bread, if an alkali is not added, the acid in the bread will stop it from browning.
Bicarbonate soda is commonly added/marinated to the meat to help soften the connective tissue and in turn give the meat a softer texture.
salt
Salt assists in removing water from food and dries them. Foods such as bacon, fish, corned beef are some examples. In the right conditions salted meat can last many years.
sugar
Sugars are used to make jams, pastes, and fruit curds. These examples of preserving fruit with acids and pectin are used in a bottling process
removal of moisture
Most food has a large percentage of water and the removal of this prevents the growth of micro-organisms as moisture is removed from food air liquid are evaporated
manipulation
Manipulation of food can mean a number of things. Any time you prepare foods such as washing, chop, mince, beat etc. you are manipulating food.
