The chemicals when added interfere with the cell membrane of the microorganisms, their enzyme activity or their genetic mechanisms. They also act as antioxidants. The common chemical preservatives permitted are 1. Benzoic acid (including benzoates) Sodium benzoate is a salt of benzoic acid and is used in preservation of colored fruit juices and squashes 2. Sulphur dioxide (including sulphites): Potassium meta-bi­-sulphite is used as a source of sulphur dioxide when it is added to the juice or squash. When used in fruits with deep colours like blue grapes, jamun, watermelon it bleaches the colour and hence in such cases benzoic acid is desirable. 3. Organic acids and their salts: Foods can be preserved by adding lactic, acetic, propionic, citric acids and their salts. Nitrates and nitrite compounds are used to preserve meat and fish products. It gives desirable colour, flavor and discourages the growth of micro-organ-isms. It also prevents toxin formation by the microorganisms in food. PROCESS Selection of fruits and vegetables (i) Fruits and vegetables should be absolutely fresh. (ii) Fruits should be ripe, but firm, and uniformly mature. Over-ripe fruits should be rejected because they are infected with microorganisms and give a poor quality product. Unripe fruits should be rejected because they generally shrivel and toughen on canning. (iii) All vegetables except tomatoes should be tender. (iv)Tomatoes should be firm, fully ripe and of deep red colour. (v) Fruits and vegetables should be free from dirt. (vi) They should be free from blemishes, insect damage or mechanical injury. INTRODUCTION Canning is defined as preservation of foods in hermetically sealed containers and usually implies heat treatment as the principal factor in prevention of spoilage. Canning was invented by Nicholas Appert in 1910 so also termed as Appertization. Foods that are canned Low acid foods: Meat, fish, poultry, dairy fall into a pH range of 5.0 to 6.8. This large group is commonly referred to as the low acid group. Acid foods: With pH values between 4.5 and 3.7. Fruits such as pear, oranges, apricots and tomatoes fall in this class. High acid foods: Such as pickled products and fermented foods. The pH values range from 3.7 down to 2.3, also Jams and Jellies are in this classification. PRINCIPLE OF CANNING Destruction of spoilage microorganism within a container by means of heat.

1. PRESERVATIVES IN FRUITS AND VEGETABLES(CHEMICAL &PHYSICAL), CANNING IN
DETAIL

2. IMPORTANCE AND PRINCIPLES OF FOOD
PRESERVATION
 Importance of food preservation
 Food production and supply does not always tally with the demand or needs of the people. In some
places, there is surplus production of food product, whereas in some other place there is inadequate
supply. It is therefore important to improve and expand facilities for storage and preservation of food to
ensure its availability and acceptability at all times.
 Principles of Food Preservation
 1. Prevention or delay of microbial de-composition.
 2. Prevention or delay of self decomposition of food
 3. Prevention of damage caused by mechanical causes, insects and rodents.

3. METHODS OF FOOD PRESERVATION IN FRUITS AND VEGETABLES
I. Physical Methods II. Chemical Methods
A. Preservation by low temperatures
1. Refrigeration
2. Freezing
B. Preservation by high temperature
1. Pasteurization
2. Canning
C. Preservation by drying
1. Sun drying
2. Drying by mechanical driers
· Spray drying
· Foam mat drying
· Drying by osmosis
· Freeze drying
D. Preservation by irradiation
A. High concentration of salt
B. High concentration of sugar
C. Using chemical preservatives

4. 1. PHYSICAL METHODS
 A. Preservation by Low Temperatures
 1. Refrigeration: The temperature maintained in the refrigerator is 0 to 5°C. Enzymatic and microbial
changes in foods are slowed down considerably. Perishable foods like eggs, dairy products, meat, sea foods,
fruits and vegetables are stored in refrigerators. Food can be stored safely for few days or a week.
 2. Freezing: The temperature of freezer is –18 to –40°C. Microbial growth is pre-vented completely and the
action of food enzymes greatly reduced. Frozen foods have better quality and needs uninterrupted supply of
electricity while storing. Foods like poultry, meat, fish, peas, vegetables, juice concentrates can be preserved
for several months by this method. In vegetables, enzyme action may still produce undesirable effects on
flavour and texture during freezing. Various methods of freezing include slow freezing, quick freezing,
cryogenic freezing and dehydro freezing.
 B. Preservation by High Temperature
 Food commodities in which pasteurization is employed include milk, beer, wines and fruit juices.
 1. Pasteurization: Pasteurization is a mild heat treatment that kills a part but not all the microorganisms
present and usually involves the application of temperature below 100°C.

5. THERE ARE THREE METHODS OF PASTEURIZATION.
 a. Bottle or Holding Pasteurization: This method is commonly used for the preservation of fruit juices.
The extracted juice is strained and filled in bottles. The bottles are then sealed air tight and pasteurized.
b. Over Flow Method: Juice is heated to a temperature about 2.5oC higher than the pasteurization temperature
and filled in hot sterilized bottles. The sealed bottles are sterilized at a temperature 2.5oC lower than filling
sealing temperature and then cooled.
c. Flash Pasteurization: The juice is heated rapidly to a temperature of about 5.5oC higher than the
pasteurization temperature and kept at this temperature for about a minute. This method has been developed
specially for canning of natural orange juice, grape and apple juice. It has the advantages of minimizing the
flavor loss and preserving the vitamins.
2. Canning:Canning is the process in which the foods are heated in hermetically sealed (airtight) jars or cans to
a temperature that destroys microorganisms and inactivates enzymes that can cause food spoilage.
The general steps to be adopted for canning foods are cleaning, blanching, filling, exhausting, sealing,
sterilizing, cooling and labeling.

6. C. PRESERVATION BY DRYING
 Both the terms ‘drying’ and ‘dehydration’ mean the removal of water. Drying is used to remove moisture by
the application of unconventional energy sources like sun and wind. Dehydration means the process of
removal of moisture by the application of artificial heat under controlled conditions of temperature, humidity
and air flow.
 Treatment of Foods Before Drying
 a. Selection and sorting for size, maturity and wholesomeness
 b. Washing, especially fruits and vegetables
 c. Peeling of fruits and vegetables by hand, machine or knife
 d. Subdivision into halves, slices, shreds or cubes
 e. Blanching or scalding of vegetables and some fruits like tomatoes and peaches
 f. Sulphuring of light coloured fruits and vegetables by exposure to sul-phur-di-oxide gas.

7.  i. Sun Drying: It is limited to regions with hot climates and dry atmosphere and to certain fruits such as raisins, prunes, figs,
apricots, pears and peaches. It is a slow process. Many Indian foods are preserved by sun drying. Papads, vadams and vathals
are made using this principle.
 ii. Drying by Mechanical Driers: Artificial drying involves the passage of hot air with controlled relative humidity over the
food to be dried or the passage of the food through such air. Fruits, vegetables, nuts, fish and meat can be successfully
preserved by this method. In the dehydration process, artificial drying methods like spray drying, vacuum drying, drum drying
and freeze drying are used for drying foods.

D. Preservation by Irradiation
 Food irradiation also known as cold sterilization is another preservation technique. The foods are bombarded by high energy rays called
gamma rays or by fast moving electrons to kill bacteria, fungi and insects and in some cases to delay fruit ripening or prevent sprouting in
onions and potatoes. The goal of irradiation is to kill the microorganisms and inactivate the enzymes without altering the food.

8. 2. CHEMICAL METHODS
 A. Salt or Brine
 It is an ancient preservation technique. Food is treated with salt or strong salt solution. Salt causes high osmotic pressure and
shrinking of cell, dehydrates foods and microbes by drawing out moisture.
 B. High Concentration of Sugar
 Sugar has the ability to bind water and make it unavailable for microbial growth. It reduces the solubility of oxygen in
moisture, which is essential for the growth and multiplication of microorganisms. Apples, oranges, guavas, grapes and
pineapples are suitable for making jams and jellies. The fruits should be just ripe because the pectin content is high in such
fruits.


9. C. USING CHEMICAL PRESERVATIVES
 The chemicals when added interfere with the cell membrane of the microorganisms, their enzyme activity or their genetic
mechanisms. They also act as antioxidants. The common chemical preservatives permitted are
 1. Benzoic acid (including benzoates) Sodium benzoate is a salt of benzoic acid and is used in preservation of colored fruit
juices and squashes
 2. Sulphur dioxide (including sulphites): Potassium meta-bi-sulphite is used as a source of sulphur dioxide when it is added to
the juice or squash. When used in fruits with deep colours like blue grapes, jamun, watermelon it bleaches the colour and hence
in such cases benzoic acid is desirable.
 3. Organic acids and their salts: Foods can be preserved by adding lactic, acetic, propionic, citric acids and their salts. Nitrates
and nitrite compounds are used to preserve meat and fish products. It gives desirable colour, flavor and discourages the growth
of micro-organ-isms. It also prevents toxin formation by the microorganisms in food.

10. CANNING IN DETAIL
 INTRODUCTION
 Canning is defined as preservation of foods in hermetically sealed containers and usually implies heat
treatment as the principal factor in prevention of spoilage.
 Canning was invented by Nicholas Appert in 1910 so also termed as Appertization.
 Foods that are canned
 Low acid foods: Meat, fish, poultry, dairy fall into a pH range of 5.0 to 6.8.This large group is commonly
referred to as the low acid group.
 Acid foods: With pH values between 4.5 and 3.7. Fruits such as pear, oranges, apricots and tomatoes fall in
this class.
 High acid foods: Such as pickled products and fermented foods.The pH values range from 3.7 down to 2.3,
also Jams and Jellies are in this classification.
 PRINCIPLEOF CANNING
 Destruction of spoilage microorganism within a container by means of heat.

11. FLOW CHART OF CANNING

12. PROCESS
1. Selection of fruits and vegetables
(i) Fruits and vegetables should be absolutely fresh.
(ii) Fruits should be ripe, but firm, and uniformly mature. Over-ripe fruits should be rejected because they are infected with
microorganisms and give a poor quality product. Unripe fruits should be rejected because they generally shrivel and toughen on
canning.
(iii)All vegetables except tomatoes should be tender.
(iv)Tomatoes should be firm, fully ripe and of deep red colour.
(v) Fruits and vegetables should be free from dirt. (vi)They should be free from blemishes, insect damage or mechanical injury.

13.  2. Grading
 The selected fruits and vegetables are graded according to size and colour to obtain uniform quality.
 This is done by hand or by machines such as screw grader and roller grader.
 Fruits like berries, plums and cherries are graded whole.
 while peaches, pears, apricots, mangoes, pineapples, etc., are generally graded after cutting into pieces or slices.
 3.Washing
 It is important to remove pesticide spray residue and dust from fruits and vegetables.
 One gram of soil contains 1012 spores of microorganisms. Therefore, removal of microorganisms by washing with water is essential.
 Fruits and vegetables can be washed in different ways. Root crops that loosen in soil are washed by soaking in water containing 25 to 50
ppm chlorine (as detergent).
 Other methods of washing are spray washing, steam washing, etc.
 4. Peeling
 The objective of peeling is to remove the outer layer.
 Peeling may be done in various ways: Hand Peeling , Steam Peeling , Mechanical Peeling, Lye Peeling

14.  5. Cutting
 Pieces of the size required for canning are cut. Seed, stone and core are removed.
 Some fruits like plum from which the seeds cannot be taken out easily are canned whole.
 6. Blanching
 Blanching is Usually done in case of vegetables by exposing them to boiling water or steam for 2 to 5 minutes, followed by cooling.
 Inactivates most of the plant enzymes which cause toughness, discoloration (polyphenol oxidase). mustiness, off-flavour (peroxidase),
softening and loss of nutritive value.
 Reduces the number of microorganisms by as much as 99%.
 7. Cooling
 After blanching, the vegetables are dipped in cold water for better handling and keeping them in good condition.
 8. Filling
 Before filling, cans are washed with hot water and sterilized
 Automatic, large can-filling machines are used in advanced countries but choice grades of fruits are normally filled by hand to prevent
bruising in India. Hand filling is the common practice.
 After filling, covering with syrup or brine is done and this process is called syruping or brining. Headspace left inside ranges from o.32 cm to
0.47 cm.

15. 9. Exhausting
The process of removal of air from cans is known as exhausting.
Exhausting methods: Thermal exhausting (SteamVacuum) , Mechanical Exhausting (Machine Vacuum)
10. Sealing
Immediately after exhausting the cans are sealed airtight by means of a can sealer.
In case of glass jars a rubber ring should be placed between the mouth of the jar and the lid, so that it can be sealed airtight
During sealing the temperature should not fall below 74°C.
11. Processing
Heating of foods for preserving is known as processing.The cans must be processed (heat treated) immediately after closing (hermetic
sealed) at suitable time and temperature Food to be canned is threatened on the one hand by bacterial spoilage (if under processed) and on
the other by danger of lower the nutritive quality by over heating .
12.Cooling
Immediately after processing, the cans are cooled in water to a temperature of 36°C to 42°C to avoid thermophilic spoilage or can rust.
If the cans are cooled much below 36°C, they may not dry thoroughly and rusting well result.
If the cans are cased at temperatures much over 42°C, thermophilic spoilage may occur

16.  13. Storage
 After labelling the cans, they should be packed in strong wooden cases or corrugated cardboard cartons and stored in a cool
and dry place.
 The outer surface of the cans should be dry as even small traces of moisture sometimes induce rusting.
 Storage of cans at high temperature should be avoided, as it shortens the shelf-life of the product and often leads to the
formation of hydrogen swell.
 ADVANTAGES OF CANNING:
 Canned food is safe to eat
 Canned food can be stored at room temperature for a long period of time.
 Canned food is concentrated food and fully edible with no wastage.
 Canned food has a longer shelf life.
 Canned food can be maintained in uniform quality.

17. THANK YOU