This document discusses various methods for preserving fruits and vegetables, including prevention of microbial growth through asepsis, low temperatures, drying, chemicals/spices; killing microbes through heat or radiation; preventing enzyme activity through blanching; and preventing damage from insects or animals through packaging. Specific preservation methods covered are filtration, fermentation/pickling, carbonation, irradiation, refrigeration, use of sugar/salt/oils as natural preservatives, high temperature treatments like pasteurization and sterilization, and drying/dehydration.

1.  Course Incharge :- Prof. R. M. Waghade Madam
 Presented By:- Shashwat P. Mahalle (PP-963)

2. PRINCIPLES AND METHODS OF FRUITS & VEGETABLES PRESERVATION
Preservation:- Preservation means extending shelf life of fresh or
processed food by using various methods and preservation or reduction of
spoilage. Preservation can be defined as the science which deals with the
methods of preventing or minimizing decay or spoilage of food (following it
to be stored in a fit condition for future use)
Principles of food preservation :-
1. Prevention or delay of microbial decomposition of food.
2. Prevention or delay of self-decomposition of the food.
3. Prevention of causes, etc. damage by insects, animals, birds, mechanical
causes etc.

3. Sr. No. Principle Methods
1 Prevention or delay of microbial decomposition
a) By keeping out the micro-
organism
Asepsis, Packing
b) By removal of micro organism By filtration
c) By hindering the growth and
activity of micro organism
Low temperature, drying,
anaerobic conditions, chemicals,
sugar, salt, acid, oil and spices etc.
d) By killing of micro organisms Heat, radiation, high presure
2 Prevention or delay of self-decomposition of the food.
a) By destruction or inactivation
of food enzymes
Blanching
b) By prevention or delay of
purely chemical reactions.
Use of antioxidants, sulphites
3 Prevention of damage by insects,
animals, mechanical causes, etc.
Packing
Methods of Preservation:-

4. The various methods used for preservation or processing vegetables
are as under.
1. Asepsis (Absence of infection) i.e. sanitation.
2. Preservation by filtration.
3. Preservation by use of preservatives (natural & chemical).
4. Preservation by low temperature or refrigeration.
5. Preservation by high temperature.
6. Preservation by drying and dehydration.
7. Preservation by carbonation.
8. Preservation by fermentation or pickling.
9. Preservation by irradiation.
10. Preservation by waxing
 Asepsis :- Asepsis means preventing the entry of microorganisms. The
inner tissues of healthy plants and animals usually are free from
microorganisms and if any microorganisms are present, they are unlikely
to initiate spoilage.
 Preservation by carbonation:- Carbonation is the process of dissolving
sufficient CO, in water or beverage so that the product when served gives
off the gas as fine bubbles and has a characteristic taste.

5. Fruit beverage are generally bottled with Co2 content varying from 1 to 8 gm/lit.
Preservation By Carbonation
 Preservation by filtration:- This method is successfully used with fruit juices,
beer, soft drinks, wine and water. In this method fruit juices are clarified by
settling or by using ordinary filters and then passed through previously sterilized
bacteria proof special filters (made up of Asbestos pad or unglazed porcelain
type of materials) which are capable of retaining yeasts and bacteria.
 Preservation by fermentation:- Decomposition of carbohydrates of
microorganisms or enzyme is called fermentation. This is one of the oldest
method of preservation.
Eg.:- Wine, Beers, Vinegar, Fermented pickles

6. Wine & Beer Vinegar
 Preservation by Irradiation:- Sterilization of food by ionizing radiation is
recently developed method of preservation which has not yet gained general
acceptance.
Irradiation Process

7. Preservation by low temperature:- Storage of fruits at low temperature help
retard microbial growth and enzyme reaction.
1) Cellar Storage:-150C
2) Refrigeration:- 0 to 50c
3) Freezing:- -180 c to -400c
Frozen Pea Refrigeration
Preservation by Preservatives:- It may be defined as any substance which
capable of inhibiting, retarding or arresting the growth of micro organisms.
A) Class – 1 Preservative:- It is also called natural preservatives. Preservative are
natural substances obtained from plants, animals or microorganism.
Eg:-
1) Sugar high concentration:- Sugar act as preservative by osmosis and not as a
true poison for micro organism. High concentration (>68%) of sugar facilates
preservation. Eg.:- Jam, jelly, Murabba, Candy

8. 2) Salt:- Exerts its preservative action by osmotic pressure resulting in plasmolysis of
microbial cells. Used for preservation of pickles. About 15-25% salt concentration
is enough to preserve fruits and vegetables.
3) Edible Oil:- In India mustard oil, rapeseed and sesame oil are generally used for
preserving fruits and vegetables. Oil on surface of fruits and vegetable pickles
create anaerobic condition which prevents the growth of micro organism.
4) Citric acid:- Citric acid is used to increase the acidity of food which then inhibit the
growth and activity of micro organism. In jam it is used at the rate 2-3%.
5) Acetic acid (Vinegar):- Acetic acid is considered to be more effective in limiting
yeast and bacterial growth than mould growth. Acetic acid checks anaerobic
fermentation. It is commonly used in the preservation of pickles, chutney, sauce
and ketchup.
Jam Pickle Sauce Candy

9. B) Class-2 Preservatives:- It is also called chemical preservative.
1) Sulphurous acid & its salts :- Potassium metabisulphite (preventive against
mould, bacteria, oxidative reaction etc.) Sulphur dioxide
2) Benzoic acid & its salts:- Sodium benzoate ( it is used in colored product 0.06-
0.1%)
 Preservation by High Temperature:-
1) Pasteurization:- Pasteurization is a heat treatment that kills partly but not all
micro organism present and the temperature is applied below 1000c.
2) Sterilization :- The heat treatment generally above 1000c for complete
destruction of all viable micro organisms on fruits & their products.
3) Blanching:- The heat treatment at about 90 to 1000c for 3 to 5 min.
Blanching
Pasteurization

10.  Preservation by drying & dehydration:- Both the term drying and
dehydration means removal of water.
Eg:-
• Sun drying :- Solar dryer
• Atmosphere drying:- Cabinet dryer, Tunnel dryer, Microwave drying etc.
Dehydrated Fruits and vegetables