This is the process of treating food to stop or slow down food decay and deterioration.
Table of Contents
Causes of Food Decay
Food spoilage and decay is brought about by:
- Bacteria
- Fungi
- Enzymes
- Oxidation
Bacteria
These are single celled micro-organisms that multiply rapidly under warm and moist conditions.
Fungi
These include the yeasts and moulds.
They thrive under warm, moist conditions.
Enzymes
They are organic catalysts that speed up rate of reaction.
They are responsible for the ripening of fruits and decay of fruits, vegetables and meat.
Oxidation
This is a reaction in which oxygen is added to a substance.
This brings about change especially in colour.
Traditional Methods
Salting
This is the use of high concentration of salt which draws water from the food.
This makes the conditions unfavourable for the thriving of micro-organisms.
Salted Meat Smoking
This is a method of using smoke from burning firewood.
The food is placed on a rack above the fireplace.
The heat partly dries the food and the smoke coats it providing a protective layer.
Examples of food which is smoked include fish, meat and maize on the cob.
Smoking Fish
Sun Drying
Drying removes moisture from food, hence depriving micro-organisms the moisture required for survival.
The food is spread on a surface under direct sunshine and is occasionally turned for complete drying e.g. grains, omena/ dagaa, meat, and some tubers.
Fermentation
This is the process of using yeast or healthy bacteria.
Yeast ferments to produce alcohol while the healthy bacteria for example in milk change the lactose into lactic acid, making the conditions unsuitable for the harmful micro-organisms.
Examples of food which are fermented are porridge and milk.
Fermented porridge
Modern methods
Refrigeration and Freezing
This involves the use of low temperatures which slow down or inactivated the action of micro-organisms.
In refrigeration the food is chilled while in freezing, there is formation of ice which solidifies the food.
Canning and Bottling
The food to be canned/ bottled is heated to kill micro-organisms and drive out air out of the jar/can.
The food is then sealed and a vacuum is created as it cools.
The vacuum prevents the re-entry of air, which may contain micro-organisms.
Pasteurization
This is the process of heating food e.g. milk to a specific high temperature for a definite length of time (in seconds).
It is then cooled immediately for storage.
The high temperature destroys the micro-organisms.
Use of Additives These are either natural or chemical substances added to food to destroy or inhibit the action of micro-organisms.
They include, sugar, vinegar, benzoic acid, sulphur dioxide and carbon IV oxide.
Irradiation
This is the exposure of food to gamma rays radiation.
The treatment kills moulds, bacteria and insects.
It also reduces the ripening and spoilage of fruits. Some of foods that are irradiated spices and condiments.
Convenience Foods
These are foods that are either partially or wholly prepared by the manufacturer.
The food is either ready to eat or requires very little preparation before eating.
Ready to eat pizza
A block of uncooked instant noodles
Examples of Convenience Foods
Partially prepared
Cake mix
Fish fillets
Coffee, cocoa
Shredded vegetables
Pastries
Wholly prepared
cakes
sodas
bread
popcorn
ready to drink juices
See also: