Food preservation

• Microorganisms spoil our food. Spoiled food emits bad smell and has a bad taste and changed color. The common methods to preserve food

Chemical Method:

• Salts and edible oils are the common chemicals generally used to check the growth of microorganisms.
• Therefore they are called preservatives.
• Sodium Benzoate and Sodium Metabisulphite are common preservatives.

Preservation by Sugar:

• Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food.

Preservation by Oil and Vinegar:

• Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment.
• Vegetables, fruits, fish and meat are often preserved by this method.

Heat and Cold Treatments:

• Boiling kills many microorganisms.
• Low temperature inhibits the growth of microbes.
• Pasteurized milk can be consumed without boiling as it is free from harmful microbes.
• The milk is heated to about 70^oC for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. It is called pasteurization.
• This process was discovered by Louis Pasteur.

Storage and Packing:

• Generally the food material is stored at low temperature.
• The temperature varies with the type of food material.
• The low temperature will not allow the microbes to grow as it inactivates the enzymes that catalyse the biochemical reactions.
•  Thus stopping the life processes of such living organisms and preventing the food material from damage.
• These days dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.
• When it is stored in air tight conditions the oxygen supply will be affected and will also effect the growth of organisms.
• Thus when food is stored in air tight containers and stored at low temperature it can prevent it from damage for a longer time.