Maharashtra Board Class 11 Food Science and Technology Chapter 8 Techniques in Food Processing and Preservation PDF Download

Techniques In Food Processing And Preservation

Food preservation is a group of methods that helps to preserve food. For thousands of years, humans have used methods of preserving food, so that they can store their food to eat it later. Food preservation helps to reduce the quantitative loss to maintain nutritional quality and to increase the availability of food.

What Is Food Preservation?

Food preservation can be defined as the science which deals with the methods of prevention of decay or spoilage of food, thus allowing it to be stored in a fit condition for future use.

Teacher's Note

When we keep jam in the refrigerator, we are preserving it so we can eat it for many days. In India, people make pickles to keep vegetables fresh for the whole year.

Exam Trick

Remember: Preservation = Keeping food fresh. Just like we keep milk in the fridge, we preserve all food to stop it from getting spoiled.

Points to Remember

Food preservation stops food from getting bad.
It helps us save money by buying food when it is cheap.
We can eat fruits and vegetables all year by preserving them.
Preserving food reduces waste in our country.

8.1 Need For Food Preservation

When food is available abundantly than our consumption, it should be preserved for future utilization. Thus, preservation activities ensure proper utilization of food. In the past, food was preserved to provide a store of food during winter, when there was no other source of food. Today, preservation of fresh produce is required for following reasons:

To increase availability of certain foods which have a short and specific growing season such as fruits and vegetables, for availing its use throughout the year.

To utilize surplus crops into value added products and prevent wastage.

To save money by preserving foods when they are most abundant, cheaper and are of good quality.

To produce such food items which are easy to store, distribute, transport and that can be made available at all places at all time.

To meet the needs of people for food in secluded and difficult areas.

To ensure constant supply of preserved food at homes, hotels and other such places.

It helps in reducing the national food loss by saving the food and improving food availability significantly.

Teacher's Note

In villages where there are no shops nearby, people preserve food so they always have something to eat. During monsoon, fresh vegetables are not available, so families use preserved vegetables.

Exam Trick

Remember: Why preserve? Answer is in four words - Money, Time, Waste, and Need. We save money, we have food anytime, we waste nothing, and we need it always.

Points to Remember

We preserve food to use it when fresh food is not available.
Preserving food saves money because we buy when prices are low.
Preserved food reaches people in far areas easily.
Food preservation stops food wastage in our country.

8.2 Principles Of Food Preservation

All food preservation methods are based upon three general principles of preventing or retarding the causes of spoilage. Those are as follows:

A. Prevention Or Delay Of Microbial Decomposition

By keeping out microorganisms (asepsis) e.g. fruit pulps in multilayer pack.

By removal of microorganisms e.g. washing or filtration etc.

By destruction of microorganisms e.g. by heat or radiation.

By slow down the growth and activity of microorganisms e.g. by using low temperature, drying, anaerobic conditions, chemicals, etc.

B. Prevention Or Delay Of Self-Decomposition Of The Food

By destruction or inactivation of food enzymes e.g. by blanching

By preventing or delay of chemical reactions e.g. prevention of oxidative rancidity with the use of antioxidant.

C. Prevention Of Damage Due To Insects, Animals, Mechanical Causes, Etc.

Teacher's Note

There are three main ways to keep food fresh: stop germs from coming, stop the food itself from changing, and protect it from insects. When you boil milk, you kill germs. When you refrigerate it, you slow down the change.

Exam Trick

Remember ABC of preservation: A = stop germs coming in, B = stop food from getting bad inside, C = protect from insects and damage. These are the three pillars.

Points to Remember

Keeping germs out means using clean containers and good packaging.
Removing germs means washing and cleaning the food first.
Killing germs means using heat or other methods.
Stopping enzymes means using cold temperature or blanching.
Protecting food means keeping it away from insects and animals.

8.3 Methods Of Food Preservation And Processing

To retain the nutritional profile alongside natural taste and aroma of a product, it is necessary to preserve it soon after preparation. Various methods of food preservation are employed and each has its own merits and demerits. The methods generally used are as under:

1. Asepsis (Keeping Out Micro-Organisms)

Asepsis means preventing the entry of microorganisms during processing, packaging and storage. The aseptic environment can be created by:

Proper packaging of the product, which protects the internal product from the surroundings.

Maintenance of general cleanliness, hygiene and sanitary conditions during processing and handling of product from raw material to finished stage.

2. Removal Of Micro-Organisms

The dust and dirt adhering to the raw material contain microorganisms and by applying various pre-treatments such as cleaning, washing, blanching, etc. help to reduce them considerably. Filtration of water, juices etc. can remove microorganisms, thereby preserve it from microbial spoilage.

3. Preservation By High Temperature

Application of heat to foods leads to the destruction of microorganisms. High temperatures used for preservation are usually:

(a) Pasteurization- temperature below 100°C (Except UHT pasteurization)

(b) Boiling - at about 100°C and

(c) Sterilization- temperature above 100°C.

One of the most important modern applications of the heat preservation is the pasteurization of milk.

Teacher's Note

When we boil milk at home, we are using heat to kill germs. In factories, they use special machines to heat milk very quickly so it stays fresh longer. This is called pasteurization.

Exam Trick

Remember: Heat kills germs. Hot water at 100°C kills most germs. Hotter heat kills all germs including tough ones. The hotter, the cleaner - but also the more loss of nutrients.

Points to Remember

Pasteurization kills some germs but not all, using low heat below 100°C.
Boiling kills germs using heat at about 100°C, like cooking at home.
Sterilization kills all germs using very hot heat above 100°C.
Pasteurization of milk keeps it fresh for many days in the fridge.
High heat kills germs but can reduce some nutrients in food.

(a) Pasteurization

The process of pasteurization was first discovered by the French microbiologist Louis Pasteur in 1862. The process uses temperature less than 100°C to eliminate pathogenic bacteria and extend shelf life of the food products. The heating may be achieved by means of steam, hot water, dry heat or electric currents and the products are cooled promptly after the heat treatments e.g. milk, wine, beer, fruit juices and aerated waters.

Blanching

Blanching is a heat treatment at about 100°C. The term is usually used in conjunction with vegetable processing, where the goals are inactivation of enzymes, reduce microflora and improve the colour. Blanching is usually performed by dipping the products in boiling water or steaming for 2-3 minutes.

(b) Boiling

Cooking of rice, vegetables, meat, fish, etc. at home is usually done by boiling the food with water and involves a temperature around 100°C.

(c) Sterilization

Sterilization is a heating process (above 121°C for 15 min) used to completely destroy all living micro-organisms in food. It can be achieved by moist heat, dry heat and irradiation heat source. Vegetables like green peas, okra, beans, etc. being non acidic and containing more starch than sugar, require higher temperature to kill the spore forming organisms.

(d) Canning

Canning is the method of preserving food from spoilage in which the foods are filled in cans heated to 115-125°C temperature and then sealed hermetically. Finally these cans are processed in boiling water for about 30 minutes and then cooled, removed and stored. They remain stable for about a year. It helps to destroy microorganisms and inactivates enzymes e.g. all kinds of canned foods such as soup, meat, beans, pulp, slices, legumes, nuts, etc.

Teacher's Note

When we buy canned food like canned mango pulp or canned vegetables, the heat and sealing keeps it fresh for months without the fridge. In India, many families use canned foods during the rainy season when fresh food is hard to find.

Exam Trick

Remember: Canning = Heat + Seal + Cool. Hot can kills germs, sealing stops new germs from coming in, and cooling keeps it safe. This is why canned food lasts so long.

Points to Remember

Canning heats food inside a sealed can to kill all germs and bacteria.
The can is sealed tightly so no new germs can get inside.
Canned food can stay fresh for about one year without the fridge.
Common canned foods are soup, meat, beans, and vegetable pulp.
Canning was invented by a French man named Nicolas Appert in 1809.

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