Food preservation

Food preservation



Food is a perishable item subjected to quick decomposition and deterioration of flavour, colour and the underlying nutritive value. As the microorganisms are growing stronger and resistant these days, conventional food preservation is of no use. Food material comes with the different levels of texture, colour, tastes making them prone for a variety of bacterial, fungal and rodent infections.

1. Introduction

2. Why do we need to preserve the food

3. Why food gets spoiled?

4. Shelf-life of a food item

5. Methods of food preservation

    5.1 Chemical Method

    5.2 Salting

    5.3 Use of edible oils 

    5.4 Sugar as a food preservative( sweetening)

    5.5 Physical methods(Heat and Cold )

    5.6 Smoking

    5.7 Canning

    5.8 Sterilization

    5.9 Dehydration

    5.10 Radiation

Why do we need to preserve the food

Since we are not able to get all varieties of food in one place, it is important to transport food from one area to the other. During transportation, it must be safely preserved. On the other hand, the bulk of produce grown by the farmers may not get the right price at the time of harvesting hence it is essential to treat them and store them in a safe place. Seasonal foods are grown according to the local climate but still, we are able to get a variety of foods, how? This is becasue we can store the foods from peak season to use them during the off-season. As the crop varieties are grown unequally becasue of the variation in the atmospheric temperatures, water types and soil types. This will result in the production of specific crops in a specified geographic area. Hence the products must be preserved and transported to the areas where there is demand. In light of this, food that is improperly stored and preserved can get spoiled. To prevent food poisoning, a scientifically sound methodology for preservation is necessary. "Food preservation is the scientific method that  prevent food spoilage,  by controlling the microbial contamination .”

Why food gets spoiled?

  1. High moisture content is good for microbial growth as they can easily adapt to the moisture condition, this is the reason fresh vegetables and fruits are quickly spoiled.

  2. Bad air surrounding the food contains a lot of microorganisms resulting in spoilage.

  3. If the food is stored for a long period of time at room temperature, the chances of food being decomposed is high.

  4. When the peel( skin)  of fruits and vegetables is exposed, it can easily attract microorganisms. 

  5. Foods containing lower levels of salt,  sugar and acid content.

  6. Insects, flies,  worms, and rats can easily spoil food.


Shelf-life of a food item

Longer the foods sustain without spoilage, loner their shelf-life. Shelf-life is the duration up to which foods remain healthy. Based on the shelf-life, food items are classified as perishable, semi-perishable and non- perishable foods

1. Non-perishable foods are whole grain cereals, nuts, pulses, and oilseeds, sugar, and jaggery.
2. Semi perishable foods fall under processed cereals and pulse products such as all-purpose flour and suji, eggs, potatoes, onions, biscuits, and baked products.
3. Perishable foods include green leafy vegetables, fruits such as apple, peas, beans, tomatoes, bananas.


Methods of food preservation

Depending on the quantity, setting and cultural practice, a variety of preservation techniques are used. In the household preservation category use of chemical method is not preferable whereas in the industrial setup, a numb er of methods such as cooling, freezing, fermenting, sun-drying canning, blanching is practised. In modern nutritional science, the following techniques of preservation are commonly seen.

1. Chemical Method: Some of the chemical preservatives; vinegar, sodium benzoate and sodium metabisulfite are used to store the food. Majority of the processed foods coming from the food industries use this strategy.

2. Salting:  Salt contains sodium, sodium discourage the growth of microbes hence it is a very good choice to store many foods. Roasted nuts and foods such as meats and fishes can be preserved by salting.

3. Use of edible oils: As the oil doesn't allow the microbes to grow, it is a great idea to add extra oil to some foods. 

4. Sugar as a food preservative( sweetening): Most of the baking foods, packed foods and certain add-ons such as jams and jellies are preserved by this method. Sugar helps to absorb the moisture content of the food thereby discouraging the microbial growth.

5. Physical methods(Heat and Cold ): Microbes will die when the foods are boiled for too long or if they are completely frozen. This is becasue majority of the microorganisms cannot tolerate extreme heat or cold. Refrigeration and boiling are the most commonly used household methods of food preservation. 

6. Smoking: Many types of meat and fish items are smoked as they kill the microbes easily. Smoke contains many anti-microbial compounds that can prohibit the growth of microorganisms.

7. Canning: An airtight container is used to store the foods by tightly closing and sealing them. Meat, fish, and fruits are preserved by canning at high temperatures.

8. Sterilization: This is done by the sterilizer. Food items such as milk is sterilized at 100°C  that can kill the microbes.

9. Dehydration: It is the process of removing excess of water from the food. Many foods can be dehydrated to keep them for longer periods. Some papads, chips, and fish are dried before transporting them.

10. Radiation; Food is exposed to rays such as UV rays, X rays and gamma rays that will break the cell wall of microbes to kill them.