Food preservation are methods of processing the food and food products to inhibit or slow down the growth of micro-organisms that cause spoilage of food. Growth of certain micro-organisms in food, leads to the loss of its nutritive value and may also make it poisonous. While processing the food for its preservation, care should be taken that its flavor and texture is kept intact, along with its nutritive value. Each type of foodstuff requires a different method of preservation. Some of the commonly used methods to preserve food against bacteria are listed below:
Canning has been in use for food preservation since early nineteenth century. Firstly, the food is boiled to destroy the bacteria and then sealed inside sterile containers like cans or jars. These filled cans are further boiled to kill any remaining bacteria. Thus, no bacteria can get into the can and spoil the food.
This is an age-old process of food preservation. Here, the water content of the food is reduced to a great extent by dehydrating the food. As a result, most of the bacteria are not be able to survive. Cereals like corn, rice, wheat, barley are preserved by the drying method. However, in some cases, the flavor and the texture of the food material changes completely because of drying. For example, raisins are formed by drying grapes.
This is a common process that is practiced, both commercially as well as domestically. Freezing completely halts all the actions of bacteria and thereby, protects the food from spoiling. It does not affect the taste of the food. In various countries, freezing is used for storing food on a large-scale, for the purpose of utilizing them at the time of emergency.
This is an ancient method of food preservation. The salt draws the moisture out of the foodstuff by the means of osmosis. As a result, the bacteria do not get suitable conditions for their growth and multiplication. Salting is particularly used for the preservation of meat, like ham and beef. Salting should be done in cold atmospheric conditions because in hot weather, salted foodstuffs may get spoiled quickly.
In this method, food is kept in some pickling agents, either to destroy bacteria or to prevent its growth. Some common pickling agents are vinegar, brine (concentrated salt water), alcohol and olive oil. This is way in which foods can be preserved for several years. It is an effective way of preserving fruits, vegetables and meat.
This method is used for preservation of liquids, especially milk. Here, milk is boiled at a specific temperature, which kills the bacteria present in it. The pasteurized milk is not only bacteria-free, but the nutritional value of milk is also retained. Other food items like juices and ice-creams can also be pasteurized in similar manner.
Some chemicals like benzoates and nitrates are also used for food preservation against bacteria. Bacteria present in foodstuffs can be killed by using radiation as well. However, many scientists debate that such foods may not be good for our health.