ZIMSEC O Level Combined Science Notes: Methods of food Preservation
The microorganisms responsible for food require water for their metabolic functions. Drying prevents respiration and causes cells to shrink it is used to preserve vegetables, fruit, milk and meat (biltong).
The food is heated/cooked and then sealed. The microorganisms responsible for going bad are killed in the process and the tinned cans also lack oxygen. This gives the food a longer shelf life. It is used with meat, fruit, vegetables and dairy products.
Salting food kills the organisms that cause food to go bad. It is used with fish (kapenta) and meat
Sugar causes the cells to shrink and prevents the growth of bacteria and fungi. For example jam.
Some of the organisms cannot survive a low pH. Some types of foods can thus be preserved in acids for example using vinegar (acetic acid) for example vegetables
Certain wood smokes produce anti-bacterial and fungicidal compounds which are used to treat meats and fish. For example apple wood is used on trout fish.
Cooling/Freezing food prevents the growth of bacteria and fungus in all foods.