Scope of Fruit and Vegetable Preservation in India:
Fruits and vegetables are an important supplement to the human diet as they provide the essential minerals, vitamins and fibre (roughage) required for maintaining health.
India with a great diversity in climatic conditions and soil types is ideal for growing a large variety of fruits and vegetables, both indigenous and introduced.
Position of India – 2nd in vegetables (1st China) and 3rd in fruits.
However for various reasons, this abundance of production is not fully utilized and wastage due to spoilage is about 20-30%.
Most fruits and vegetables are seasonal and perishable in nature. In a good season there may be a glut but because of insufficient transport facilities, lack of good roads and poor availability of packaging materials, the surplus cannot be taken quickly enough to markets in urban areas.
Moreover the surplus often cannot be stored for sale in off-season because of inadequate local cold storage facilities. Thus, the cultivator do not get a good price for their produce.
Although, the R and D efforts on the development of post-harvest handling has helped in reducing the spoilage, considerable losses continue to occur.
Two approaches are possible for solving this problem.
(i) One is the creation/expansion of cold storage facilities in the fruit and vegetable producing regions, as also in the major urban consumption centres, to ensure supply of fruit and vegetable throughout year.
(ii) Another approach is to process the fruits and vegetable into various products which could be preserved for a long time and add value to the product.
With increasing in purchasing power of middle class, there is increasing demand for factory made jams, gullies, pickles.
In spite of all these, the fruit and vegetable preservation industry of present is able to utilise less than 2% of the total production for conversion into products like canned fruits, juices and their beverage squashes etc. as against 40% in developed countries. Thus there is considerable scope for expansion of the industry, which in turn would give a fillip to development of horticulture, specially in hilly areas and through export of value-added products, earn more foreign exchange.
India is one of the cheapest producer of horticultural produce. If the Government addresses some of the gaps in processing industry, Indian economy will get a boost up.
(i) Most of the varieties grown in India are not suitable for processing.
(ii) Seeds of processble varieties can be imported and multiplied using tissue culture technique.
(iii) Lowering sales tax on agriculture produce may help the industry to grow.
(iv) In New Exim Policy of Union Government, setting of Agriculture Export Zones (AEZ) to identify each state’s competitive advantage and to promote the cultivation and processing of fruit and vegetable accordingly.
Principles and Methods of 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.
It is better if the following directions are kept in mind to control the spoilage.
1. Raw materials should be thoroughly examined and handled hyginically to avoid microbial spoilage.
2. Equipments must be cleaned every time before use.
3. Processing should take place as soon as possible after sealing of cans or bottles.
4. Use of contaminated coater should be avoided.
5. The finished products after canning or bottling should be stored in well-ventilated rooms in a cool and dry place.
Freshly prepared products are highly attractive in appearance and possess good taste and aroma, but deteriorate rapidly if kept for sometime. This is an account of several reasons.
(i) Fermentation caused by moulds, yeasts and bacteria.
(ii) Chemicals present in pulp/juice, may react with one another.
(iii) Air coming in contact with the product, may deteriorate.
(v) Traces of metal from the equipment may get into the product and spoil its taste and aroma.
In the preservation of foods by various methods, the following principles are involved:
1. Prevention or delay of microbial decomposition
(a) By keeping out micro-organisms (asepsis).
(b) By removal of micro-organisms e.g. by filtration.
(c) By hindering the growth and activity of micro-organisms.
(d) By killing the micro-organisms e.g. by heat or radiation.
2. Prevention or delay of self decomposition of food
(a) By destruction or inactivation of enzymes e.g. by blanching.
(b) By prevention or delay of chemical reactions e.g. prevention of oxidation by means of an antioxidant.
3. Prevention of damage by insects, animals, mechanical causes
To retain the natural taste and aroma of a product, it is necessary to preserve it soon after preparation, without allowing it to stand for any length of time. The product must be prevented from the damage of insect and animals and prepare transportation and packaging must be ensured to protect the food products from any mechanical problems.
Methods of Preservation:
1. Asepsis (Absence of infection):
Asepsis means preventing the entry of Microorganisms. Maintaining of general cleanliness while, picking, grading, packing and transporting of fruits and vegetables increases their keeping quality and the products prepared from them will be of superior quality.
Sun-drying or mechanical drying of fruits and vegetables involves complete removal of the moisture from them. They are then treated with sulphur fumes to maintain colour and also to avoid spoilage by Microorganisms. Dates, Grapes, Jack, Peaches, beans, bitter gourd, Onions, Potatoes etc. are preserved by this method.
When fruits and vegetables are brought suddenly to a very low temperature at which all the chemical reactions stop. But it requires rather expensive equipment and stripping and storing under refrigeration.
4. Preservation by heating:
This process consists basically the application of heat in varying degrees to the food in close containers for a sufficiently long time to sterilise the contents before they are hermetically sealed. This method of preservation by heat is also known as processing. Canned fruits and vegetables come under this category.
High temperature used for preservation:
(i) Pasteurization temperature (below 100 °C)
(ii) Sterilization temperature (above 100 °C).
5. Preservation by sugar:
No organisms can grow on a substance which contains sugar concentration above 65%, as they get desiccated by osmosis. Jams, Jellies, marmalades, candies, crystallized fruits are preserved by this method.
6. Preservation by salt:
Products which contain about 15% salt makes it most unfavourable for the growth and multiplication of Microorganisms. Salt acts both by osmosis and as a poison on Microorganisms. Pickles of fruits, vegetables and other pickles products are preserved by this method..
7. Preservation by chemicals:
Chemicals like Benzoic acid S02 at specific concentration help to preserve the fruit juices and squashes. Benzoic acid in the form of 0.06-0.10% sodium benzoate is sufficient and is effective against yeasts and its action is effective in the presence of CO2.
Potassium matabisulphite (KMS) when added liberates SO2 which reacts with water to form sulphurous acid. The concentration of SO2 recommended is 350 PPM. It is more active against moulds, spores and bacteria.
8. Preservation by fermentation:
Fruit juices containing sugar are fermented to produce alcohol. These fermented substances keep off the spoilage organisms due to the presence of alcohol. 14% alcohol acts as preservative in wines. Wines, beer, vinegar, fermented drinks, fermented pickles etc. are, prepared by these processes.
9. Preservation by irradiation:
Sterilization of food by ionising radiations is a recently developed method of preservation which is yet to gain acceptance. In the irradiation of food, the radiation dose must be carefully controlled. The WHO and IAEA have recommended that radiation dose of upto 1 kilo rad is not hazardous. Radiation energy must be provided in such a manner that it reaches every particle of food to ensure adequate killing of all microorganisms.
Ionizing radiations can be used for sterilisation of food in hermetically sealed packs, reduction of the spoilage flora on perishable foods, control of infection in stored cereals, prevention of sprouting of potatoes, onions etc.
Jam is more or less a concentrated fruit pulp possessing a fruity heavy body form. It is rich in flavour. Pectin in the fruit gives it a good set.
It contains not less than 68% soluble solids and thus high concentration of sugar facilitate preservation.
Jam manufacturer can chose fresh fruit, frozen, chilled or cold stored fruits, fruits or fruit pulp preserved by heat, sulphite, fruits or fruit pulp or dried fruits.
Sound fresh fruits free of any damage and for better felling effect, green fruits should be mixed with the ripe fruits. Overripe fruit should not be used.
The fruit must be washed thoroughly to remove any adhering dust.
Leaves, stalks and other undesirable portions of the fruits must be removed.
Fruit is then subjected to preliminary treatment which varies from fruit to fruit, e.g. apples are peeled, cut into pieces and then pulbed. Strawberries are crushed between rollers but in stone, fruits pacts, they are Lye peeled, stones removed and pulp is cut into pieces.
Addition of sugar:
Amount of sugar to be added depends upon the degree of ripeness and acidity of the fruit. To get a minimum of 68.5% of sugar in the jam, generally 55.0 g of sugar is added to every 450 g of fruit.
Addition of acid, colour, and flavour:
Generally citric acid, tartaric acid are used to supplement the acidity of fruits for jam making because appropriate combination of Pectin, sugar and acid is essential to give a set to the jam. A good result is obtained if the pH of mixture is about 3.0.
Ordinarily, jams do not require addition of flavours of desired, may be added when jam boiling in hearing completes. Looking fruit and sugar mixture are boiled to concentrate the soluble solids to about 68.5% and also to bring about necessary degree of inversion of sugar.
Determination of soluble solids is easily carried out by using hand refractometer while, boiling is in progress.
Soon after the end point is reached the jam should be cooled in cooling pan to about 93 °C and filled into jars at this temperature either mechanically or by hand. The surface of the jam in the jars should be covered with a thin disc of waxed tissue paper and allowed to cool. The jars should be stored in a dry place.
Jams can be prepared from fruits like apple, tomato, papaya, strawberry etc.
In Jelly making, pectin is the most essential constituent. This pectin is present in the cell walls of fruit. Precipitation of pectin while boiling causes jelly formation. Precipitation takes places, only when pectin, acid, sugar and water are in equilibrium.
Fruits for jelly:
Many fruits are rich in pectin as well as acid and are thus well suited for jelly making. Apple, grape, guava, lemon, orange, plum are rich in pectin and acid.
Selection of fruits:
Sufficiently ripe, but not overripe and should have good flavour. Fruits are washed thoroughly with water. Guava and apple, need not be peeled, while fruits like, orange, lemon require peeling before used.
Extraction of pectin:
Only a minimum quantity of water should be used to the fruit for a simple extraction of pectin the amount of water required depend or the kind of fruit.
To get the desired pectin requirements the fruit should be cooked. The cooking time also varies from fruit to fruit and the time of boiling of fruit required to extract pectin.
The pectin extract can be clarified by allowing to settle overnight and the supernatant pectin liquor separated as it may be filtered through a muslin cloth. Aluminum vessels are used for boiling.
Usually about 0.5-1.0% pectin of suitable quality in the extract is sufficient to produce a good jelly. If pectin is in excess of this a firm and tough jelly is formed and if it is less the jelly may fail to set.
Pectin, sugar, acid and water must be present approximately in the following proportion, pectin (1.0%), sugar (60-65%), fruit acid (1%) water (33-38%).
The sugar should be sprinkled on the fruit extract while it is boiling and should be thoroughly mixed by stirring to ensure complete dissolution. During boiling, the scum which rises to the top is removed.
Cooking of Jelly:
The mixture is boiled for about 20 minutes and the end point is when the final Brix reaches 65°C. The end point can also be determined by flake test.
After training the end point, jelly is then cooled slightly and poured into hot and dry containers.
The preservations of food in common salt or vinegar is called pickling. Spices and oil may be added. Pickles are good appetizers and add to the partibility of a meal. They aid digestion by stimulating the flow of gastric juices.
Salt, vinegar and lactic acid are the three important ingredients used in pickling. These substances when used in sufficient quantities, act as preservatives either singly or collectively.
Vegetables don’t foremast when covered with a large amount of salt.
This preservative as pickles, the final percentage should not be below 2%. To avoid dilution of vinegar by water from vegetables they can be kept in a strong vinegar of about (10% concentration).
3. Lactic acid:
Sufficient quantity of lactic acid, prevents lactic acid bacteria, and any change in the composition of the material is prevented, provided it is air-tight.
Pickling process: Two stages
1. Dry softening:
Vegetable is prepared, washed thoroughly and weighed. For every 100 kg of prepared vegetables 3 kg of salt is used. The vegetable is placed about a few cm and a small quantity of salt and another layer of vegetables thick layer is placed. This process of keeping the vegetables and sprinkling the salt is continued till 3-quarter of the barrel full. The top of the vegetable is sealed with a choose cloth and placed every a clean stone to give some weight to the vegetables placed in. The container is kept in a warm dry place and fermentation is allowed to proceed. In a short time juice from the vegetable forms the brine covering the whole mases. Fermentation then starts and is usually complete in about 8-10 days. This may be confirmed by tapping the containers gently.
2. Fermentation in brine:
Soaking of the vegetable in salt solution of predetermined concentration for a certain length of time is called brining. This treatment is given only to vegetables like cucumber which do not contain sufficient juice, to form brine with dry salt.
Problems in pickle making:
1. Bitter taste, (due to use of strong vinegar or excess spice).
2. Dull and faded product (insufficient curing, inferior quality).
3. Shivelling (when fruit and vegetable directly placed in strong sugar, vinegar or salt.
4. Swin formation: White swin always form on the surface, vegetable in brine.
5. Softness and stipperiness: Inadequate, covering with brine.
6. Blackening: Fe in the brine equipment used in pickling.