Use Of Chemical Preservatives
Preservatives are defined as chemical agents which serve to retard, hinder or mask the undesirable changes in food. These changes may be caused by micro organisms, by enzymes of food or by purely chemical reactions.
Certain chemicals when added in small quantities can hinder undesirable chemical reaction in food by:
1. Interfering with the cell membrane of the microorganism, their enzyme activity or their genetic mechanism.
2. Acting as antioxidants.
Maximum amounts allowed to be added to each type of food is regulated by law because higher concentrations can be a health hazard. Benzoic acid in the form of its sodium salt is an effective inhibitor of moulds and is used extensively for the preservation of jams and jellies.
Some of the other chemical preservatives used are:
1. Potassium metabisulphite
2. Sorbic acid
3. Calcium propionate
4. Sodium benzoate
The development of off-flavours (rancidity) in edible oils is prevented by the use of Butylated Hydroxy Anisole(BHA), Butylated Hydroxy Toluene(BHT), lecithin which are some of the approved antioxidants.
Radiant energy can be used to preserve food. Gamma rays and beta particles produced by special electronic machines are sources of energy used to preserve food.
These waves penetrate throughout the food. As the waves and particles pass through the food, they collide with molecules in the food and in microorganisms. These result in chemical alterations. The goal of irradiation is to kill the microorganism and inactivate the enzymes without altering the food.
Changes in the food are minimized if it is done in a vacuum, and if ascorbic acid is present. Berries and meat are preserved in this way.