The nutrients that give us energy and help us maintain good health also cause our food to spoil. There are innumerable microorganisms 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 microorganisms 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 Preserving Food
Food preservation is not just helpful in keeping the nutrients of food intact, but is also a smart way to cut down on costs. Here are a few technique that may come in handy.
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 and Refrigeration
Microorganisms 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 and Bottling
In this process, the food is first processed and then sealed in airtight containers. While the microorganisms 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.
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 microorganisms is arrested and food is preserved. Nuts are usually preserved by this method.
Salt is a natural food preservative that draws out moisture from the food as well as from the cells of the microorganisms 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.
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 microorganisms 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.
This is a process where liquid food is preserved. Before, pasteurization was done to combat the souring of local wines, however, it is mostly done to milk now. The milk is heated for 15 to 30 seconds at around 158°F as the bacteria present in the milk will get killed. Then, it is quickly cooled at 50°F in order to prevent the rest of the bacteria from growing. The next step is to store the milk in sterilized bottles and stored in a cool place.
Oil and Vinegar Preserving
Oil and vinegar are common in Italian cooking. However, this isn't the only place where the duo is utilized. The mixture of oil and vinegar is used to prevent the growth of microorganisms that spoil the food. So vegetables and fruits are preserved in them so they can last for a longer time.
This is a very simple method where perishable food items are smoked in order to increase their shelf life. The food, mostly fish and meats, is cured (salting) and then exposed to smoke created via wood. Certain fruits and vegetables can also be smoked and preserved.
The process of fermentation was not invented, but discovered. Certain foods such as cheeses, wines, and beers can be preserved for a long time as their production is done by specific microorganisms. They fight against less benign organisms that spoil the food. In this process, beginner microorganisms, salt, hops, temperature control, and specific oxygen levels are used to create conditions that will help the organisms produce food which is fit for our consumption.
Preserving fruits is an age-old process that is still continued worldwide. The fruits are boiled so that the moisture content is reduced and the unwanted bacteria are killed. Then, the process of sugaring is done in order to prevent any regrowth of bacteria, followed by sealing the final product in an airtight, sterilized jar. The final step is vital as it prevents the jam from getting contaminated.
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.
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 microorganisms.