Food preservation

Introduction

Food preservation

Food is a perishable item vulnerable to  decomposition which can cause the deterioration of flavour, colour and its underlying nutritive value. As the microorganisms are becoming more powerful and resistant these days, the conventional food preservation techniques are no more valid. A variety of food material exist in different textures, colours, tastes which can make the food vulnerable for a number of bacterial, fungal and rodent spoilage.

 

Why do we need to preserve the food

Food production and availability is subjective and they depend on many factors. 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 store them in a safe place so that they can be sold at a higher prices later. Furthermore, some of the seasonal foods are grown according to the local climate but still, the majority of us have access to the variety of foods, this is because these foods were stored and then distributed equally in all seasons. Additionally, the crops varieties are not grown uniformly across various geographic areas as each one vary in term of the atmospheric temperatures, water types and soil types. This results in the unequal distribution of crop varieties across various geographic areas. Therefore, the products must be preserved and transported from the low demand areas to the high-demand areas. But this is possible if the food can be stored and transported safely. To prevent food spoilage, a scientifically sound methodology of food preservation is crucial. "Food preservation is the scientific method that  prevent food spoilage,  by controlling the microbial contamination.”

 

Why food gets spoiled?

  1. High moisture content creates a conducive atmosphere for microbial growth as they can easily adapt to the moisture condition.

  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, higher is the 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 of food available, cost of storage  and the local cultural practices , a variety of food preservation techniques are in use. In the household preservation category, the  use of chemical methods are not the preferable strategies whereas, in the industrial setup, a number of methods such as cooling, freezing, fermenting, sun-drying, canning and blanching are practised. According to the guidelines provided by the food and nutrition boards, the following techniques of food preservation are common in practice.

1. Chemical Method: They use  chemical preservatives such as vinegar, sodium benzoate and sodium metabisulfite to store the food. Majority of the processed foods coming from the food industries adopt this strategy.

2. Salting:  Salt contains sodium, which discourage the growth of microbes hence salt is a very good choice to store many foods. Roasted nuts ,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 top-ups such as jams and jellies are preserved by using this method. Sugar helps to absorb the moisture content of the food thereby discouraging the microbial growth.

5. Physical methods (Heat and Cold ): Microbes die when the foods are boiled for too long or if they are completely frozen. This is because 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 the smoke kills 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 through canning at high temperatures.

8. Sterilization: This is carried out by a 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.

 

 

Read more

1.        

Animal husbandry

2.

Single cell proteins

3.

Recommended dietary intake                    

4.

Nutrient cycle

  

 

Important questions

  1. What are the factors contributing to the spoilage of foo?

  2. Why do we need to preserve the food?

  3. Classify foods based on the shelf-life of foods.

  4. Enlist the food preservation techniques and explain any 3 food preservation techniques.

  5. List the most suitable household food preservation techniques, and explain.

  6. Identify any 10 local foods and prepare a table detailing preservation  methods suitable for each food items.

 

 



img-1


img-1


img-1

Course List