Food Preservation Methods
Millions of fruits and vegetables are produced each year and they are lost due to poor processing and preservation. Fresh fruits are abundant during the season and are not available during off season. Due to this the food has to be stored until the next season. Fish and meat too have to be pre-served as all that is killed or caught cannot be eaten at one time. Bacteria, fungi and yeasts tend to decay the food and render it unfit to eat. Hence all fresh foods have to be preserved if it is to be used after a period of time.
Besides when food spoils, they undergo physical and chemical changes that results in the food becoming inedi-ble or hazardous to eat. The chief causes of food spoilage are;
· The growth of microorganisms like bac-teria, yeast and moulds.
· The action of enzymes that normally occur in the food.
Other causes of spoilage are non enzy-matic reactions in food such as oxida-tion and mechanical damage such as bruising and damage from rodents and insects.
In order to prevent food spoilage and ensure food security and availabil-ity, various food preservation techniques have been used over the several years. The earliest steps in food preservation are drying of grains and nuts. Later salting, smoking and drying were applied to pre-serve the food.
Food preservation is known as “the sci-ence which deals with the process of pre-vention of decay or spoilage of food thus allowing it to be stored in a fit condition for future use”.
Preservation also can be defined as “the state in which any food may be retained over a period of time without being contaminated by pathogenic organ-isms or chemicals, without losing opti-mum qualities of colour, texture, flavour and nutritive value”.
Food production and supply does not always tally with the demand or needs of the people. In some places, there is surplus production of food product, whereas in some other place there is inadequate sup-ply. It is therefore important to improve and expand facilities for storage and pres-ervation of food to ensure its availability and acceptability at all times.
· Increase in shelf life of foods.
· Availability of seasonal foods through-out the year.
· Stability in prices of food as there will not be a deficit in supply.
· Good quality
· Edibility – texture and flavour
· Retention of nutritive value
· Retention of original colour of food.
For the process of preservation, a preservative (e.g. salt, sugar, vinegar) is needed.
· By keeping out microorganisms and preventing contamination from pathogens. It involves apply-ing the strictest rules to minimize the risk of infection (asepsis).
· Removal of microorganism through usage of membrane which retains microorganisms (filtration).
· By hindering the growth and activity of microorganisms (refrig-eration, dehydration, addition of chemical preservatives).
· By killing microorganisms (boiling, irradiation).
· By destruction or inactivation of enzymes (blanching).
· By prevention or delay of chemical reactions (anti oxidants).