User:Nileshwaribai/sandbox

=FOOD PRESERVATION=

Food preservation is the name for a number of processes that help to preserve food. This means that the food treated that way will go bad (spoil from bacteria) later that if it had not been treated that way. For thousands of years, humans have used methods of preserving food, so that they can store food to eat later.

IMPORTANCE
Food production and supply does not always tally with the demand or meets of the people. In some places there is surplus production of a food product, whereas in some other place there is inadequate supply. Even foods are perishable and semi-perishable like juicy fruits, vegetables, mangoes, tomato, papaya and many more, which very quickly gets spoilt. It is therefore important to improve and expand facilities for storage and preservation of food. Food preservation helps in:

1. Increasing the self-life of foods thus increasing the supply. So many perishable foods can be preserved for a long time.

2. Making the seasonal food available throughout the year.

3. Adding variety to the diet.

4. Saving time by reducing preparation time and energy, as the food has already been partially processed.

5. Stabilising prices of food, as there is less scope of shortage of supply to demand.

6. Decreasing wastage of food by preventing decay or spoilage of food.

7. Improving the nutrition of the population. Preserved foods help people to bring a variety in the diet, thereby decreasing nutritional inadequacies.

=PRINCIPLES OF FOOD PRESERVATION=

Preservation of food by any method is based on the following principles:

(A)Prevention or delay of microbial decomposition
(i)By keeping out micro-organisms (asepsis)

Nature provides protective coverings around the food in the form of shells of nuts, die skins of fruits and vegetables, the shells of eggs, and the skin or fat on meat or fish. These protective coverings act as a preservative factor, thereby preventing or delaying microbial decomposition.

Even in the food industry several aseptic methods are adopted to prevent the contamination of foods during its processing. In the canning industry, the load of micro-organisms determines the heat process necessary for the preservation of food. This is better known as aseptic canning. In the dairy industry, the quality of milk is judged by its bacterial content.

Packaging of foods is also an application of asepsis. The cover­ings may range from simple wrappers to hermetically sealed contain­ers of canned foods. Polythene bags and moisture proof wrappings in­cluding heavy foil, heavily mixed papers and cellophane are used.

(ii). By removal of micro-organisms

Filtration is a method used for the complete removal of micro­organisms and is successfully applied only to clear liquids such as water, fruit juices, beer, soft drinks and wine. The filter used in this method is made of asbestos pads, unglazed porcelain and similar materials. This filter is sterilised and made “bacteria proof” before being used as a filtration device. The liquid is filtered by forcing it under pressure through the filter.

(iii). By hindering the growth and activity of micro-organisms

This may be done by low temperature or drying or by providing anaerobic conditions.

When anaerobic (absence of oxygen) conditions are created, some aerobic organisms die while the spores of others may survive but are unable to multiply in the absence of oxygen. This principle is used as a preservative factor in canned and packaged foods.

Low temperature at which foods are preserved in cold storage slows down and sometimes prevents bacterial activity.

Drying of foods is a very effective method of avoiding spoilage of food, since micro-organisms cannot flourish in the absence of moisture.

Certain chemicals like sodium benzoate and potassium metabi­sulphite may be used for preservation, but they should be used with great care as an excess of any of them may result in poisoning.

(iv). By killing the micro-organisms using heat or radiation

In this process gamma rays or high speed electrons are used to destroy the micro-organisms. Both types of radiations are termed as ionized radiations. This topic will be dealt with in detail under “Methods of Food Preservation”.

(B) Prevention or delay of self decomposition of food
This is done by destruction or inactivation of food enzymes by blanching. The inactivation affects many plant enzymes which otherwise might cause toughness and change in colour. All plant and animal tissues contain enzymes which are highly active at room temperature and above. For each 10° C (19°F) raises in temperature the rate of the chemical change doubles. Rancidity of fats is an excellent example of undesirable oxidation and leads to the deterioration in flavour of foods that may contain only small quantities of fat. Oxidation also leads to a loss of ascorbic acid. Plant and animal tissue fiber is softened, the surfaces of cut non-acid fruits are oxidised and become darkened as a result of enzyme action, thereby changing the colour, texture and nutritive value.

Before freezing (to prevent the growth of bacteria) fruits and vegetables are blanched to inactivate the oxidative enzymes, Blanch­ing is done with hot water or steam and the extent of treatment applied varies with the kind of food being treated. The brief heat treatment is supposed to accomplish reduction of the number of micro-organisms on the food, enhancement of the green colour of vegetables such as peas and spinach, and prevention of damage because of mechanical causes, insects and animals.

Items of food can be damaged either by insects and animals or by mishandling. Therefore, meticulous care should be exercised to minimize any damage to the foods. The entire operation of preserving foods is divided into three stages of careful handling:

i. Proper packaging

ii. Quick and effective transportation

iii. Providing good storage facilities, like silos for grains and cold storages for fruits and vegetables.

=METHODS=

Drying
The most ancient food of preservation methods, drying is a great way of preserving herbs, fruits, vegetables and meats. Since the beginning of time people have let sun and nature take care of drawing moisture out of foods. This practice is used throughout the world. For example, Southern Italy is known for drying tomatoes while India is known for drying chilies, mangos and a host of spices.

To dry herbs, simply tie them together and hang in a sunny spot away from any humidity. To dry fruits or vegetables, set them out on a clean surface and keep them in the sun for a few weeks (this only works well in dry, warm climates). A more modern method of drying is to use an electric dehydrating machine.

Salting
Salting is a sub category of the drying method. The main difference here is that salt is added to products, mainly meat and fish, to draw out moisture. This lowers the bacteria content and makes food adaptable for later use. Adding salt to animal protein turns it into a bit leathery. Popular foods made in this tradition are beef jerky and dry salted cod.

Canning
In order to can foods, you need heat. The canning technique was developed by a French chemist during 1795 and was used to preserve food for Napoleon's army. Canning is a popular way of preserving fruits, vegetables and meats.

Both cans and glass jars are suitable for canning. The important thing will be to sterilize your recipients in simmering water for a few minutes (this includes lids). Then they will be ready to be filled with things like jam. After filling, place the lid on firmly but not too tight. To finalize the process lower the jars into a pot full of water, cover and bring to a boil. Process for about 10 minutes. Pull the jars out of the hot water and let cool. They will vacuum seal as they cool. Cooking times vary per recipe.

Pickling
The main difference between this category and canning is that you need two things for pickling: salt and acid. Pickling requires you soak your produce, most famously cucumbers, in a brine with salt. When they have pickled for the desired amount of time you transfer them to a jar full of vinegar. At this point you can use the canning method to produce a vacuum seal, if you wish.

A bonus of pickling is that it does not change the texture too much. The vegetables undergo a fermentation process, which also results in a vitamin boost. Pickled vegetables are known for having an increased level of vitamin B6.

Freezing
In the olden days, people would carry ice down from a neighboring mountain. Of course, now we use electric freezers to preserve our foods. Freezing changes the texture of most fruits and some vegetables but meats and fish fair well. In the summer time, you may want to freeze your berries so that you have them available for smoothies or baking later in the year.

The best way to do this is freeze fruit in batches (the same method would apply to vegetables). For instance, scatter fresh berries on a baking tray and put it in the freezer. After they have frozen solid, put them in a bag. This will avoid clumps of berries that are impossible to separate without thawing.

=ADVANTAGES=

Food preservation has the following advantages:

1. Food preservation prevents the food from being spoiled by the action of enzymes and microorganisms.

2. Food preservation increases the safe storage period of foodstuffs. 3. It increases the availability of out of season foodstuffs. 4. It increases the availability of various foodstuffs even at distant and not easily approachable places. In other words, it makes the transportation of the food materials easier.

5. Food preservation makes up for the deficiencies in the diet.