The Microbial World_ Food Preservation

The Microbial World_ Food Preservation

Multiple Choice

1.Citrus canker diseases is caused by ____________.

• a) bacteria

• b) virus

• c) protozoa

• d) fungi

Multiple Choice

3.A disease caused by protozoa and spread by a mosquito is ____

• a. Dengue

• b. Malaria

• c. Polio

• d. Measles

Multiple Choice

1.Which of the following method is not used for preserving food?

• a) freezing

• b) smoking

• c) fermentation

• d) pickling

Open Ended

BIG QUESTION: Have you ever wondered why jams, jellies and squashes contain lots of Sugar?

Learning Objective

Explain the methods used to preserve food.

Bacteria and Fungi

• Bacteria and fungi are decomposers . They produce certain toxic substances.

• When bacteria and fungi come in contact with food, they begin to decompose the food and release chemical toxins.

• This makes the food contaminated or spoilt and unfit for consumption.

• If such contaminated food is consumed it can lead to development of symptoms of food poisoning, such as nausea , vomiting , abdominal cramps and diarrhoea.

TASK: Identify various techniques that can be used for preserving food from spoilage

Create a mindmap using bubble.us, draw.io or any other online tool.

METHODS USED TO PRESERVE FOOD

• HEATING

  COOLING

  ADDING SALT OR SUGAR

  DEHYDRATION

  ADDING OIL OR VINEGAR

  CHEMICAL PRESERVATIVES

  CANNING AND VACUUM PACKING

  PASTEURISATION

Explain different ways by which food can be preserved.

Heating

Microbes can be killed by boiling the milk and water.

Milk is prepared in the factories ,using the technique known as Ultra Heat Treatment.

In this , partial sterilization of milk is done by heating it at about 135⁰C for few seconds. Sterilization destroys all microorganisms on the surface of an article or in a fluid to prevent disease transmission. When milk is heated to such high temperatures, it kills more bacteria than by traditional method of heating. 

Once packed ,this milk stays for several months 

Cooling

The growth of microorganism slows down when they are kept in cold environment.

Thus cooling the food items minimizes the spoilage of food by allowing down the growth of microbes.

Placing the food in a refrigerator at about 5 ⁰C is a common method which delays the spoilage of food for a few days.

A deep freezer provides a temperature as low as -18⁰C which can prevent the food from getting spoiled for a few months .

Refrigeration only delays but does not completely rule out the possibility of food spoilage.

Adding Salt and Sugar

The Presence of salt or sugar in the food items reduces the moisture content of the food . Also prevents the growth of microbes in food items.

Also, the microorganism tend to loose water from their bodies in the process of excess salt or sugar in food, through a process known as Osmosis.

This prevents the growth of microbes on the food items.

That is why common salt is widely used as a preserving agent to preserve food items such as pickles , meat, fish and chips.

Jams, jellies and squashes are preserved by adding sugar in them. 

Dehydration

It is the process of removing water. Since water is one of the prerequisites for microbial growth , drying food items helps in preserving them .

Eg:- cereals , pulses , dry fruits and spices can be preserved by this method

Adding oil or vinegar

Creates an unfavorable environment for the growth of microbes.

Fish, pickles meat are preserved by this method.

Chemical Preservatives 

Chemical preservatives such as sodium benzoate and sodium metabisulphite are used to preserve jams, sauces and ketchups.

This inhibits the growth of microbes and there by increase the shelf life.

Canning and Vacuum packing.

Canning is done to package or preserve the food by putting in sealed , airtight t containers.

Also in vacuum packing method the air is removed from the packet and then sealed . This enhances the life of food products.

Pasteurization

This technique is mainly used in the dairy industry to preserve milk.

This milk is known as pasteurized milk.

This technique is discovered by Louis Pasteur.

Heating milk at 72⁰ C for 15 seconds and suddenly cooling it.

Sudden heating and cooling kill microbes present in the milk , which then can be stored in packets or containers.

Open Ended

Why do we keep a refrigerator in our home?

CHALLENGES:

• 1.Draw a mind map to show the various methods of food preservation.

• 2.Explain the method of pasteurization

• 3.A well –preserved body of a mountaineer was found buried under the snow in Himalayas on way to Mt. Everest . It is believed that the body had been lying for more than 15 years . How do you think the body remained preserved for so long.

• 4. Zubin bought a fried rice and decided to have the meal on the next day. He put the food on the table. On the next day, the food was smelly and the rice's texture changed. Give an inference based on the observation on the food.

• 5.Design a pamphlet on food safety and health- Extension Question

Let's Reflect

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