Food Preservation: Methods of Preserving Food

The nutrients that give us energy and help us maintain good health also cause our food to spoil. There are innumerable micro-organisms in the atmosphere that derive their nutrition from these nutrients by breaking them into simpler forms. As these minute life forms start disintegrating the nutrients, they set off the process of food spoilage. With the knowledge of the role that micro-organisms play in spoiling food, a number of methods of food preservation have been developed by man. All these methods work by altering conditions like temperature, availability of water or oxygen in the food, or in the environment in which the food is stored. Changing or altering these factors hinders the growth of these minute organisms, and hence prevents food spoilage.

Methods of Preservation of Food

Drying: This is one of the oldest methods of food preservation. This process acts by reducing the moisture content in the food which in turn arrests bacterial growth. Drying is largely used for preserving meat. However, fruits and vegetables can also be preserved by this method. The additional advantage of drying is that it reduces the size and weight of the food product, therefore making it more portable. Sun drying, oven drying, and drying with the help of a dehydrator are the various ways used to reduce the water content of food.

Freezing: Micro-organisms require a certain level of temperature for their survival. Freezing foods lowers the temperature to levels that make the environment unsuitable for microbial growth. This is the principle on which home refrigerators work. Cold stores are used to preserve large amounts of food stuff for a longer period of time, so that they can be used during a natural calamity or national emergency. The only drawback of this food preserving technique is its dependence on electricity.

Canning: In this process, the food is first processed and then sealed in airtight containers. While the micro-organisms are killed by processing the food, their entry and proliferation is restricted by canning it in an airtight environment. The various methods used to process the food before it is canned are pasteurization, boiling, freezing or vacuum treatment.

Vacuum Treatment: In this method food is stored in airtight containers that strips bacteria of the oxygen that helps it carry on with its metabolism. Hence, the growth of these micro-organisms is arrested and food is preserved. Nuts are usually preserved by this method.

Sugaring: Sugaring is used to preserve fruits like apples, apricots and plums in sugary syrup that dehydrates the foods. The skin of certain fruits are cooked in sugar till they crystallize and then they are stored in a dry environment. One drawback of this method is that sugar itself draws moisture. Once the amount of moisture in sugared foods rise, it might reach the level congenial for microbial growth.

Salting: Salt is a natural food preservative that draws out moisture from the food as well as from the cells of the micro-organisms that may be present in it. Lack of moisture kills these organisms and hence prevents food spoilage. Salt is commonly used as a preservative in meat products.

Pickling: Cucumber, beef, peppers and some vegetables may be preserved by pickling. This technique involves dipping the food in some liquid chemical that prevents the growth of micro-organisms but still maintains edibility of the food. The preserving liquids used are vinegar, brine, alcohol and some other oils. This process is known as chemical pickling. The other way of pickling is by fermentation. In fermentation pickling, the preservation agent is produced by the food itself during the process of fermentation.

These are a few of the healthy ways to preserve food. Most of these can be domestically used to delay food spoilage. In other methods, ionizing radiation, high pressure and even controlled growth of certain bacteria are used to fight the decaying action of micro-organisms.