Food preservation methods are necessary to protect harvests of food crops from spoilage due to fungal or bacterial colonization (and/or insect and rodent infestation) as well as preventing oxidation, especially of fats.
Main methods of food preservation are:
- drying desiccation so that there is not enough water to support microbial life.
- Salting adding salts so that water will be drawn out of the microbes and they will not be able to live or multiply. (through osmotic pressure across the cell walls of microbes) 10% salt in water is enough to prevent microbial growth.
- Candying (or preserving in syrup). adding or concentrating sugars so that water will be drawn out of the microbes and they will not be able to live or multiply. (through osmotic pressure across the cell walls of microbes) 80% sugar and above kills all but the yeasts - which will be dormant above this concentration.
- Alcohol Fermentation converts the sugars to alcohols, which prevent microbial growth.
- Adding alcohol.
- sugars convert first to alcohol by the acton of yeasts, and then into acetic acid which slows microbial activity.
- Pickling by adding acids such as vinegar.
- Alkali - by addition of lye such as in hominy or lutefisk
- Canning - sterilizing with heat (and sometimes pressure) sometimes in combination acidity or sugar and maintaining food in a sealed sterile environment
Drying is one of the most common methods of food preservation in use today. One of the primary advantages of cereal grains, oil seeds, nuts and pulses is that they easily and readily dry for long-term storage in grain bins or silos. Drying is also effective for the preservation of herbs.
Silage and Haylege (acid)
Ensilage is a common form of fermentation for the preservation of silage for animal fodder, it is frequently used in areas where rainfall and humidity make it difficult to produce hay. (how to make silage) Silage is commonly kept in silos, ether of the upright type or horizontally on the ground or in pits. On a small scale a barrel with a tightly sealing lid can be used. main article making silage