Preservation processes, including canning, drying, pasteurising, freezing and fermenting.
Watch the adjacent video on food preservation in the 1800's.
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CANNING
There is evidence to suggest that foods were preserved in earthenware jars by the people from ancient Egypt and Central America. A process was developed int he 1700's whereby food was placed into wide mouthed corked bottles which were heated in boiling water. 100 years later more advanced materials such as glass, pottery and tin were being used as containers. The first use of the traditional canning process was by Nicolas Appert in 1806.
Summary of the Canning process:
SELECTION-> The selection is done according to size, shape, texture, flavor and maturity.
CLEANSING-> Moving belts place foods under high pressure sprays, removing dirt, dust, chemicals and organisms.
GRADING AND SORTING-> Food is sorted and packed according to characteristics; size, shape and colour.
PEELING AND CORING-> Done manually or by machine when required.
BLANCHING-> Done before canning, foods are immersed in boiling water or exposed to steam, inactivating enzymes, softening plant tissue and in some cases removing any air withing the fruit.
FILLING-> Sterilised cans are filled to within 1cm from the top.
EXHAUSTING/ PREHEATING-> Uses heat to make the food expand, creating a vacuum that seals the food.
Summary of the Canning process:
SELECTION-> The selection is done according to size, shape, texture, flavor and maturity.
CLEANSING-> Moving belts place foods under high pressure sprays, removing dirt, dust, chemicals and organisms.
GRADING AND SORTING-> Food is sorted and packed according to characteristics; size, shape and colour.
PEELING AND CORING-> Done manually or by machine when required.
BLANCHING-> Done before canning, foods are immersed in boiling water or exposed to steam, inactivating enzymes, softening plant tissue and in some cases removing any air withing the fruit.
FILLING-> Sterilised cans are filled to within 1cm from the top.
EXHAUSTING/ PREHEATING-> Uses heat to make the food expand, creating a vacuum that seals the food.
THE FOLLOWING VIDEO SHOWS THE CANNING PROCESS IN REFERENCE TO CANNING CORN.
DRYING
By dehydrating foods we are also dehydrating the microorganisms, as microorganisms contain approx 80% moisture. Freeze drying is the most effective method used, it involves; the food being rapidly frozen then broken into small pieces and placed on trays, then using a vacuum environment and gentle heat, the ice crystals sublimate (change from a solid straight to a vapor without a liquid phase), this leaves dehydrated pieces that are ground into foods such as instant coffee, tea and soup.
PASTEURISATION
Pasteursation is exposing foods to a high temperature, usually more then 60*c and less then 95*c in order to kill pathogens and substantially reduce the number of spoilage microorganisms. There is a variety of different pasteurising procedures that heat for different lengths of time, e.g, HTST (high temp short time), LTLT (low temp long time), and UHT (Ultra high temp). Shorter heating times result in improved flavour. Foods preserved by this method include fruit juice and milk.
FREEZING
Freezing involves the storage of feeds between the temperatures of -15 to -30*c. The process of freezing makes and water present unavailable, and therefore makes it unavailable for microbial growth, this process also inactivates but does not kill enzymes. The speed of freezing a food product is critical to the quality of it. A slow freezing process forms larger ice crystals then a fast process, and upon thawing, cell rupture can occur, causing a deterioration of the food product.
FERMENTATION
Fermentation is a biological preservation process that produces alcohol or acid through the action of microorganisms such as yeast, mould and acid-producing bacteria. E.g, In wine making, the build-up of alcohol when fruit is combined with the microorganism yeast eventually stops the growth of the yeast and stabilises the wine. Other foods that use this process include yoghurt, cheese, soy sauce and bread.