MICROORGANISMS
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Microorganisms: The tiny organisms which are not seen with unaided eye are called microorganisms or microbes. They may be unicellular or multi-cellular. Among these only fungus can be seen with unaided eye or with the help of a magnifying glass. Others can not be seen with unaided eye. These microbes can live in all kinds of environment, ranging from ice cold climate to hot springs and deserts to marshy lands. The study of microorganisms is known as microbiology.
Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. Virus, though different from these four are considered microbes.
Bacteria: Bacteria are the simplest unicellular organisms. These are plant like. They may exist singly or in chains or groups. To survive unfavorable environmental conditions, a bacterium develops a thick outer wall and is called a spore. The size of bacteria varies from 0.2 to 100 micron ( I micron = 1/1000th mm = 10-3 mm).
Shapes of Bacteria –There are three types of bacteria based on their shape.
1. Bacilli. (singular bacillus). Rod-like bacteria are called bacilli.
2. Cocci. (singular coccus) Spherical-shaped bacteria are called cocci.
3. Spirilla (singular, spirillum) Spiral-shaped bacilli are called spirillum.
Examples of some bacteria are Escherichia coli, Diplococcus pneumonial.
The Diseases Caused by Bacteria
Disease Causative agent Discoverer
Leprosy (Hansen's Disease) Mycobacterium leprae G. A. Hansen, 1873
Tetanus Clostridium tetani A. Nicolaier, 1884
Whooping Cough Bordetella pertussis J. Bordet and O. Gengou, 1906
Typhoid Fever Salmonella typhi C. J. Eberth, 1880
Cholera Vibrio cholorae R. Koch, 1883
Plague Yersinia pestis S. Kitasato, A.T. E. Yersin, 1894
Tuberculosis Mycobacterium tuberculosis R. Koch 1882
Meningitis Neisseria meningitidis A. Weichselbaum, 1887
Bacterial Pneumonia Streptococcus pneumoniae A. Fraenkal, 1886
Anthrax Bacillus anthracis R. Koch, 1877
Bacterial Dysentry Shigella dysenteriae K. Shiga, 1898
Diarrhoea Escherichia coli T. Escherich, 1885
Food Poisoning Salmonella enteriditis A. A. H. Gaertner, 1888
Diphtheria Corynebacterium diphtheriae T. A. E. Klebs, 1883
Tooth Decay Streptococcus mutans
Tonsillitis Streptococcus pyogenes
Gasteroenteritis Escherichia coli
Plant diseases caused by bacteria:
Leaf Blight of Rice and citrus canker are caused by xanthomonas bacteria.
Usefulness of bacteria.
Bacteria are used in cleaning up of the environment. For example, the organic wastes like vegetable peels, remains of animals and plants, faeces etc are decomposed in to harmless and usable substances by bacteria.
Types of Algae
Brown Algae ( Diatoms)
Red Brush Algae
Hair AlgaeGreen Algae
Blue Green Algae
Beard Algae
Examples of Algae:
Chlamydomonas ( one-celled), Laminaria, Nostoc,Ulva, Spirogyra, Cymbella
Fungi: Fungi live everywhere-in the air, in water, on land in soil, and in and on plants and animals. Some fungi are microscopic and some others are not. Fungi are heterotrophic, saprophytic and parasitic. The storage carbohydrate of fungi is glycogen. Largest fungus is Giant puff ball.
There are four types of fungi.
1. Yeast: (Unicellular & live in colonies), required for bread & cake, pastries making and also used for commercial production of alcohol and wine.
2. Mildew : ( Unicellular)
3. Moulds: (Multi-cellular): Antibiotic like penicillin is prepared from moulds named Penicillium.
4. Mushroom:
Diseases caused by fungus: Late blight of potato and rust of wheat, Ring worm and scabies are fungal diseases of human.
Protozoa: In Greek, proton means first and zoa means animals. Protozoa are unicellular organisms. They are animal-like and the smallest of all animals. They exist in water and soil. They may be free living or exist as parasites. They have various locomotory organs like pseudopodia, cilia and flagella. They digest their food in compartments called vacuoles. Examples:- amoeba, paramecium, giadia
Diseases caused by protozoa:- Malaria, Dysentery.
Virus: Viruses are very small in sizes. They are microscopic. Viruses are quite different from other microbes. They reproduce only inside the host organism like bacterium, plant or animal cells. The scientists regard viruses as a link between living and non-living. The diseases caused by viruses are Chicken pox, polio, Hepatitis A, Cold, Influenza (flu) & Cough etc.
Plant diseases: Yellow vein mosaic of bhindi, Leap curl of papaya
IMPORTQNT POINTS:
Antibiotics
The medicines which kill or stop the growth of the pathogens are called antibiotics. Antibiotics are available in the form of tablets, capsules or injections. A number of antibiotics like Streptomycin, tetracycline and erythromycin, ampicillin, amoxicillin are produced from bacteria and fungi. Penicillin was the first antibiotic.
The following precautions must be taken while taking antibiotics.
Harms caused by microorganisms
Some microorganisms are beneficial while some are harmful. The harmful or disease-causing microorganisms are called pathogens. Pathogens enter our body through air, water, food, physical contact or animals. The details of the diseases caused by microorganisms are as below.
Bacteria cause diseases like Tuberculosis, Cholera, Typhoid, Tetanus, Plague, Anthrax
Diarrhoea etc in humans and Citrus Canker in plants. Viruses cause diseases like Measles, Chicken pox, Polio, Hepatitis A etc in humans and Yellow vein mosaic of bhindi in plants. Protozoa causes Malaria, dengue etc. Fugi cause many skin diseases.
Food Poisoning
Food poisoning is caused by the consumption of food spoilt by the toxic substances produced by the microorganisms. This makes the food poisonous causing serious illness, even may be fatal.
Vaccines: A vaccine helps a body prepare in advance to fight against any disease. Vaccines are usually a very mild dose of the disease-causing virus or bacteria which has been weakened or killed. These vaccines stimulate the body to create antibodies against a particular infection. Antibodies are substances in the blood that destroy bacteria, viruses or other harmful agents. When a weakened or dead pathogen is introduced into the bloodstream, antibodies are formed. Once a person receives a vaccine and develops immunity, he or she is usually protected for life. The process of taking vaccine is called vaccination. The diseases which can be prevented by vaccination are hepatitis A, hepatitis B, influenza and rabies etc. Childhood diseases like diphtheria, measles, mumps, pertussis (whooping cough), polio, tetanus and chickenpox can also be prevented by vaccination.
USEFULNESS OF MICROORGANISMS:
Commercial use of Microorganisms:
1. Microorganisms like yeast are used for commercial production of alcohol and wine.
FERMENTATION: The process of conversion of sugar into alcohol is called fermentation. In this process, yeast is grown on natural sugars present in grains like barley, wheat, rice, crushed fruit juice etc. Then sugar is converted into alcohol by yeast.
FORMATION OF CURD: During curd formation, lactobacillus bacterium converts sugar of milk into lactic acid. Then lactic acid causes curdling of milk and gives sour taste to curd. The formation of good quality of curd depends upon the right type of starter, containing lactobacilli. Starter is a small amount of earlier batch of curd that is added to warm milk for purpose of setting of curd. The lactobacilli of the starter get activated and multiply. The best temperature for the lactobacilli to start multiplying in the milk is close to the human body temperature, i.e. between 30-40 degrees Celsius. Milk is then covered and kept undisturbed in a warm place. After 4-10 hours, curd is formed.
COMMUNICABLE OR CONTAGIOUS DISEASES: Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable or contagious diseases. Examples of communicable diseases are cholera, common cold, chicken pox and tuberculosis.
Disease causing microorganisms are called pathogens. Pathogens enter our body through air, water, food, direct physical contact, carriers and cuts and wounds etc.
FOOD PRESERVATION: The process of treating food to slow down or stop the growth of microorganisms that spoil food is called food preservation. Salts, edible oils, sodium benzoate and sodium metabisulphite are common preservatives.
NATURAL PRESERVATIVES:
1. SALT: Salt is used as a preservative in pickles. It is also used to preserve meat and fish for ages. Meat and fish are covered with dry salt to check the growth of bacteria. Salt is also used to preserve amla, raw mangoes, tamarind etc. Due to the presence of salt in the food, water comes out of the food by the process of osmosis. When there is no water or less water in the food, the microbes are not able to grow and food becomes safe.
2. SUGAR: Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food. Preservatives like Sodium benzoate and sodium metabisulphite are also used for the preservation of jams and squashes.
3. OIL & VINEGAR: Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such environments. Vegetables, fruits, fish and meat are often preserved by the use of oil and vinegar.
5. HEATING: Heating the food to a high temperature kills the microbes living in it.
6. REFRIGERATION AND FREEZING: Refrigeration and freezing of food slow down the activity of bacteria which all foods contain. The food thus stays fresh longer. Mushrooms, milk, milk-based sweets, meat and meat products are preserved by this method.
7. DRYING AND DEHYDRATION: Drying and dehydration is the oldest method of food preservation. Drying reduces moisture necessary for bacteria growth that causes deterioration. This process is done through sun drying, or through solar and electrical oven drying. Mushrooms, onion, cauliflower, green beans, apricots, bananas, cherries meat, fish and prawns are preserved by this method.
8. CANNING: Canning is a method of preserving food in which the food is processed and sealed in airtight containers (cans). Before sealing, the food is sterilized by suitable methods to kill the microbes.
PASTEURISATION: The milk is heated to about 700 C for 15 to 30 minutes to destroy disease causing microorganisms and then suddenly chilled to a temperature about 40 C to retard the growth of surviving microorganisms and stored. This process of heating and chilling is called pasteurization. Pasteurized milk can be consumed without boiling as it is free from harmful microbes.
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Microorganisms: The tiny organisms which are not seen with unaided eye are called microorganisms or microbes. They may be unicellular or multi-cellular. Among these only fungus can be seen with unaided eye or with the help of a magnifying glass. Others can not be seen with unaided eye. These microbes can live in all kinds of environment, ranging from ice cold climate to hot springs and deserts to marshy lands. The study of microorganisms is known as microbiology.
Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. Virus, though different from these four are considered microbes.
Bacteria: Bacteria are the simplest unicellular organisms. These are plant like. They may exist singly or in chains or groups. To survive unfavorable environmental conditions, a bacterium develops a thick outer wall and is called a spore. The size of bacteria varies from 0.2 to 100 micron ( I micron = 1/1000th mm = 10-3 mm).
Shapes of Bacteria –There are three types of bacteria based on their shape.
1. Bacilli. (singular bacillus). Rod-like bacteria are called bacilli.
2. Cocci. (singular coccus) Spherical-shaped bacteria are called cocci.
3. Spirilla (singular, spirillum) Spiral-shaped bacilli are called spirillum.
Examples of some bacteria are Escherichia coli, Diplococcus pneumonial.
The Diseases Caused by Bacteria
Disease Causative agent Discoverer
Leprosy (Hansen's Disease) Mycobacterium leprae G. A. Hansen, 1873
Tetanus Clostridium tetani A. Nicolaier, 1884
Whooping Cough Bordetella pertussis J. Bordet and O. Gengou, 1906
Typhoid Fever Salmonella typhi C. J. Eberth, 1880
Cholera Vibrio cholorae R. Koch, 1883
Plague Yersinia pestis S. Kitasato, A.T. E. Yersin, 1894
Tuberculosis Mycobacterium tuberculosis R. Koch 1882
Meningitis Neisseria meningitidis A. Weichselbaum, 1887
Bacterial Pneumonia Streptococcus pneumoniae A. Fraenkal, 1886
Anthrax Bacillus anthracis R. Koch, 1877
Bacterial Dysentry Shigella dysenteriae K. Shiga, 1898
Diarrhoea Escherichia coli T. Escherich, 1885
Food Poisoning Salmonella enteriditis A. A. H. Gaertner, 1888
Diphtheria Corynebacterium diphtheriae T. A. E. Klebs, 1883
Tooth Decay Streptococcus mutans
Tonsillitis Streptococcus pyogenes
Gasteroenteritis Escherichia coli
Plant diseases caused by bacteria:
Leaf Blight of Rice and citrus canker are caused by xanthomonas bacteria.
Usefulness of bacteria.
Bacteria are used in cleaning up of the environment. For example, the organic wastes like vegetable peels, remains of animals and plants, faeces etc are decomposed in to harmless and usable substances by bacteria.
- Bacteria are used in the preparation of medicines. For example, a number of antibiotics and vaccines are produced from bacteria.
- Rhizobium bacteria present in the nodules of their ( of leguminous plants) roots, fix atmospheric nitrogen and increase the soil fertility.
- Lactobacillus bacterium promotes the formation of curd.
- Acetobacter bacteria promote preparation of vinegar.
Types of Algae
Brown Algae ( Diatoms)
Red Brush Algae
Hair AlgaeGreen Algae
Blue Green Algae
Beard Algae
Examples of Algae:
Chlamydomonas ( one-celled), Laminaria, Nostoc,Ulva, Spirogyra, Cymbella
Fungi: Fungi live everywhere-in the air, in water, on land in soil, and in and on plants and animals. Some fungi are microscopic and some others are not. Fungi are heterotrophic, saprophytic and parasitic. The storage carbohydrate of fungi is glycogen. Largest fungus is Giant puff ball.
There are four types of fungi.
1. Yeast: (Unicellular & live in colonies), required for bread & cake, pastries making and also used for commercial production of alcohol and wine.
2. Mildew : ( Unicellular)
3. Moulds: (Multi-cellular): Antibiotic like penicillin is prepared from moulds named Penicillium.
4. Mushroom:
Diseases caused by fungus: Late blight of potato and rust of wheat, Ring worm and scabies are fungal diseases of human.
Protozoa: In Greek, proton means first and zoa means animals. Protozoa are unicellular organisms. They are animal-like and the smallest of all animals. They exist in water and soil. They may be free living or exist as parasites. They have various locomotory organs like pseudopodia, cilia and flagella. They digest their food in compartments called vacuoles. Examples:- amoeba, paramecium, giadia
Diseases caused by protozoa:- Malaria, Dysentery.
Virus: Viruses are very small in sizes. They are microscopic. Viruses are quite different from other microbes. They reproduce only inside the host organism like bacterium, plant or animal cells. The scientists regard viruses as a link between living and non-living. The diseases caused by viruses are Chicken pox, polio, Hepatitis A, Cold, Influenza (flu) & Cough etc.
Plant diseases: Yellow vein mosaic of bhindi, Leap curl of papaya
IMPORTQNT POINTS:
- Bacteria are single-celled.
- Some algae are single-celled, some are multi-cellular.
- Protozoa are single-celled.
- Fungi are multi-cellular.
- Amoeba can live alone.
- Fungi and bacteria live in colonies.
- Some microorganisms are beneficial and some others are harmful and cause diseases.
- The disease-causing microorganisms are called pathogens.
- Bacteria are used in cleaning up of the environment.
- Bacteria are used in the preparation of medicines.
- Rhizobium bacteria present in the nodules of their ( of leguminous plants) roots, fix atmospheric nitrogen and increase the soil fertility.
- Lactobacillus bacterium promotes the formation of curd.
- Acetobacter bacteria promote preparation of vinegar.
- Yeast reproduces rapidly and produces carbon dioxide during respiration.
- Yeast is used for commercial production of alcohol and wine.
- Yeast is unicellular & lives in colonies and is required for bread & cake, pastries making.
- The process of conversion of sugar into alcohol by yeast is called fermentation.
- Louis Pasteur discovered fermentation in 1857.
- The medicines which kill or stop the growth of the pathogens are called antibiotics.
- A number of antibiotics like Streptomycin, tetracycline and erythromycin, ampicillin, amoxicillin are produced from bacteria and fungi.
- Antibiotics are available in the form of tablets, capsules or injections.
- Alexander Fleming discovered penicillin.
- When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader.
- Edward Jenner discovered the vaccine for small pox in 1798.
- The bacteria and algae which fix atmospheric nitrogen are called biological nitrogen fixers.
- Microbial diseases that can spread from and infected person to a healthy person through air, water, food or physical contact are called communicable diseases.
- Cholera, common cold, chicken pox and tuberculosis are communicable diseases.
- Female Anopheles mosquito carries parasite of malaria.
- Female Aedes mosquito carries dengue virus.
- Robert Koch discovered Bacillus anthracis bacterium which causes anthrax disease.
- Foot and mouth disease of cattle is caused by a virus.
- Leaf Blight of Rice and citrus canker are caused by xanthomonas bacteria.
- Late blight of potato and rust of wheat are caused by fungi.
- Yellow vein mosaic of Bhindi is caused by virus.
- The chemicals generally used to check the growth of microorganisms are called preservatives.
- Sodium benzoate and sodium metabisulphite are common preservatives and are used in the jam and squashes.
- Common salt is used as a preservative for fish, meat, amla, raw mangoes and tamarind.
- Sugar is used as preservative for jams, jellies and squashes.
- Oil and vinegar are used as preservative for vegetables, fruits, fish and meat.
- The process of pasteurization was discovered by Louis Pasteur.
- Antibiotics are not effective against cold and flu as these are caused by viruses.
- Poliomyelitis is better known as polio.
- Polio is a highly contagious viral disease.
- Smallpox has been eradicated by vaccination through worldwide campaign against it.
- The process of pasteurization was discovered by Louis Pasteur.
Antibiotics
The medicines which kill or stop the growth of the pathogens are called antibiotics. Antibiotics are available in the form of tablets, capsules or injections. A number of antibiotics like Streptomycin, tetracycline and erythromycin, ampicillin, amoxicillin are produced from bacteria and fungi. Penicillin was the first antibiotic.
The following precautions must be taken while taking antibiotics.
- Antibiotics must be taken only on the advice of qualified doctor.
- The course prescribed by the doctor must be completed.
- The antibiotic must not be taken in wrong doses otherwise it may make the drug less effective when one needs it in future.
- The antibiotic must not be taken unnecessarily as it may kill the beneficial bacteria in the body.
Harms caused by microorganisms
Some microorganisms are beneficial while some are harmful. The harmful or disease-causing microorganisms are called pathogens. Pathogens enter our body through air, water, food, physical contact or animals. The details of the diseases caused by microorganisms are as below.
Bacteria cause diseases like Tuberculosis, Cholera, Typhoid, Tetanus, Plague, Anthrax
Diarrhoea etc in humans and Citrus Canker in plants. Viruses cause diseases like Measles, Chicken pox, Polio, Hepatitis A etc in humans and Yellow vein mosaic of bhindi in plants. Protozoa causes Malaria, dengue etc. Fugi cause many skin diseases.
Food Poisoning
Food poisoning is caused by the consumption of food spoilt by the toxic substances produced by the microorganisms. This makes the food poisonous causing serious illness, even may be fatal.
Vaccines: A vaccine helps a body prepare in advance to fight against any disease. Vaccines are usually a very mild dose of the disease-causing virus or bacteria which has been weakened or killed. These vaccines stimulate the body to create antibodies against a particular infection. Antibodies are substances in the blood that destroy bacteria, viruses or other harmful agents. When a weakened or dead pathogen is introduced into the bloodstream, antibodies are formed. Once a person receives a vaccine and develops immunity, he or she is usually protected for life. The process of taking vaccine is called vaccination. The diseases which can be prevented by vaccination are hepatitis A, hepatitis B, influenza and rabies etc. Childhood diseases like diphtheria, measles, mumps, pertussis (whooping cough), polio, tetanus and chickenpox can also be prevented by vaccination.
USEFULNESS OF MICROORGANISMS:
Commercial use of Microorganisms:
1. Microorganisms like yeast are used for commercial production of alcohol and wine.
- Acetobacter bacterium is used for commercial production of acetic acid (vinegar).
- Clostridium bacterium is used for commercial production of Acetone.
- Some bacteria and fungi are used for commercial production of antibiotics and vaccines.
- Lactobacillus bacterium is used for commercial production of curd, cheese etc in diary industries.
- Bacteria are also used for production of pickles.
- Yeast is used for commercial production of breads, pastries and cakes in baking industries.
- Bacteria are used in cleaning up of the environment. For example, the organic wastes like vegetable peels, remains of animals and plants, faeces etc are decomposed in to harmless and usable substances by bacteria.
- Some bacteria and blue algae increase the soil fertility. Rhizobium bacteria present in the nodules of their (of leguminous plants) roots, fix atmospheric nitrogen and increase the soil fertility. These microbes are commonly called biological nitrogen fixers.
FERMENTATION: The process of conversion of sugar into alcohol is called fermentation. In this process, yeast is grown on natural sugars present in grains like barley, wheat, rice, crushed fruit juice etc. Then sugar is converted into alcohol by yeast.
FORMATION OF CURD: During curd formation, lactobacillus bacterium converts sugar of milk into lactic acid. Then lactic acid causes curdling of milk and gives sour taste to curd. The formation of good quality of curd depends upon the right type of starter, containing lactobacilli. Starter is a small amount of earlier batch of curd that is added to warm milk for purpose of setting of curd. The lactobacilli of the starter get activated and multiply. The best temperature for the lactobacilli to start multiplying in the milk is close to the human body temperature, i.e. between 30-40 degrees Celsius. Milk is then covered and kept undisturbed in a warm place. After 4-10 hours, curd is formed.
COMMUNICABLE OR CONTAGIOUS DISEASES: Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable or contagious diseases. Examples of communicable diseases are cholera, common cold, chicken pox and tuberculosis.
Disease causing microorganisms are called pathogens. Pathogens enter our body through air, water, food, direct physical contact, carriers and cuts and wounds etc.
- Through Air: Common cold, Influenza (flu), Chicken Pox, Mumps, and Measles etc. are caused by viruses (viral diseases) and are transmitted through air. Tuberculosis and diphtheria and Pertussis are caused by bacteria (bacterial diseases) and are transmitted through air.
- Through Food and water: Hepatitis A, Amoebiasis, and giardiasis are caused by protozoa and are transmitted through contaminated water and food. Cholera, typhoid, salmonellosis and botulism are caused by bacteria and are transmitted through contaminated water and food.
- Through direct physical contact:: Trachoma ( in the eyes) and leprosy are caused by bacteria ( bacterial diseases) and are transmitted by direct physical contact. Ring worm and scabies mite are caused by fungi (fungal diseases) and are transmitted through direct physical contact.
- Through Carriers: There are some insects and animals which act as carriers of disease-causing microbes (pathogens). House fly, female Anopheles mosquito (vector of malaria parasite), female Aedes mosquito (vector of dengue virus) are carriers or vectors. Human louse is the carrier of a bacterial disease called typhus fever. Bacterial diseases like plague and leptospirosis are transmitted by Rodents.
- Through Cuts and wounds: Tetanus bacteria and virus of AIDS can be transmitted through cuts and wounds on skin.
FOOD PRESERVATION: The process of treating food to slow down or stop the growth of microorganisms that spoil food is called food preservation. Salts, edible oils, sodium benzoate and sodium metabisulphite are common preservatives.
NATURAL PRESERVATIVES:
1. SALT: Salt is used as a preservative in pickles. It is also used to preserve meat and fish for ages. Meat and fish are covered with dry salt to check the growth of bacteria. Salt is also used to preserve amla, raw mangoes, tamarind etc. Due to the presence of salt in the food, water comes out of the food by the process of osmosis. When there is no water or less water in the food, the microbes are not able to grow and food becomes safe.
2. SUGAR: Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food. Preservatives like Sodium benzoate and sodium metabisulphite are also used for the preservation of jams and squashes.
3. OIL & VINEGAR: Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such environments. Vegetables, fruits, fish and meat are often preserved by the use of oil and vinegar.
5. HEATING: Heating the food to a high temperature kills the microbes living in it.
6. REFRIGERATION AND FREEZING: Refrigeration and freezing of food slow down the activity of bacteria which all foods contain. The food thus stays fresh longer. Mushrooms, milk, milk-based sweets, meat and meat products are preserved by this method.
7. DRYING AND DEHYDRATION: Drying and dehydration is the oldest method of food preservation. Drying reduces moisture necessary for bacteria growth that causes deterioration. This process is done through sun drying, or through solar and electrical oven drying. Mushrooms, onion, cauliflower, green beans, apricots, bananas, cherries meat, fish and prawns are preserved by this method.
8. CANNING: Canning is a method of preserving food in which the food is processed and sealed in airtight containers (cans). Before sealing, the food is sterilized by suitable methods to kill the microbes.
PASTEURISATION: The milk is heated to about 700 C for 15 to 30 minutes to destroy disease causing microorganisms and then suddenly chilled to a temperature about 40 C to retard the growth of surviving microorganisms and stored. This process of heating and chilling is called pasteurization. Pasteurized milk can be consumed without boiling as it is free from harmful microbes.