This document discusses various methods for preserving fruits and vegetables, including drying, canning, freezing, and controlled atmospheric storage. It describes specific drying techniques like sun drying, mechanical drying, osmotic dehydration, and freeze drying. Canning involves high heat processing in sealed containers to kill microbes. Freezing preservation works below -18°C to inhibit microbial growth. Controlled atmospheric storage precisely controls gas levels to extend shelf life. The document also covers packaging materials and modified atmospheric packaging techniques for preserved foods.

2. PRESERVATIVES
• Preservatives are defined as "chemical agents,
which serve to retard, hinder or mask
undesirable change in food".
• These changes may be caused by
microorganisms, by the enzymes of food, or
by purely chemical reactions.

3. NEED OF PRESERVATION
• When the availability of food is more than the
present use it is preserved for future
consumption.
• Preservation helps the food to be available in
off-season and in any place.

4. PRINCIPLES OF PRESERVATION
• Prevention or delay of microbial decomposition
• Keeping out microorganisms (asepsis)
• Removal of microorganisms e.g. by filtration.
• Hindering the growth and activity of microorganisms e.g. by
low temperature, drying, anaerobic conditions or
chemicals.
• Killing the microorganisms e.g. by heat or radiations.
• Prevention or delay of self decomposition of food
• Destruction or inactivation of food enzymes e.g. by
blanching.
• Delay of chemical reactions e.g. by prevention of oxidation
by means of an antioxidant.

5. METHODS OF PRESERVATION
• Temporary preservation: In this method growth
of microorganisms is only retarded or inhibited
for short time like steeping preservation, with
chemical preservatives. Two chemical
preservatives.
Potassium metabisulphite
Sodium benzoate
• Permanent preservation: In this method the
growth of spoilage microorganisms are
completely destroyed by different means like,
drying, canning, freezing etc

6. CANNING
• Canning involves the application of
temperatures (to food) that are high enough
to destroy all microorganisms present in
sterilized containers to prevent re-
contamination and to preserve the food.
Canned fruit

7. SHELF-LIFE OF PROCESSED PRODUCTS
• Normally at ambient conditions of storage the
processed products will have a minimum shelf
life of 6 months. Canned products will have
one year shelf life at ambient conditions of
storage itself. The shelf life of others can be
doubled by storing at refrigerated conditions.

8. DRYING

9. DRYING OF FRUITS
The methods of fruit and vegetable drying are
 Sun drying
 Drying by mechanical driers,
 osmotic dehydration,
 Spray drying,
 Foam mat drying,
 Freeze drying.

10. SUN DRYING
• Sun drying is an old and traditional method of
drying. It is limited to climates with a hot sun and
a dry atmosphere and to certain fruits such as
raisins, prunes figs, apricots, pears and peaches.
It is a slow process. Vegetables like french beans,
curd chilli are preserved by this method.
• Fruit bars, raisins, dehydrated products from
fruits like fig, pomegranate and vegetables like
onion, carrot, cauliflower, okra, mushrooms etc.

11. Sun drying

12. Mechanical dryer

13. Osmotic dehydration
• The moisture is drawn out from all cell tissues. The
water is then bound with the solute, making it
unavailable to the microorganisms. In osmotic
dehydration of fruits, the method involves the partial
dehydration of fruits by osmosis in a concentrated
sugar solution or syrup.
• Fruits such as apple, banana, cherry, citrus, grapes,
guava, mango, papaya, pineapple, plum, etc. Osmotic
Dehydration can remove 30-50% of the water from
fresh ripe fruits e.g mangoes, pineapple, banana,
sapota and papaya etc.

14. Osmotic drying

15. • SPRAY DRYING
Thin fruit juices
like pine apple,
citrus are dried to
a powder in spray
driers in which
the liquid is atomized
and sprayed into a
hot air stream for
almost instant drying.

16. Freeze dryer

17. Freeze drying
• Freeze drying is a method of drying involving
freezing and then the sublimates of the ice
under vacuum. Removal of water from a
product while it is frozen by sublimation is
called freeze drying. Fresh flavours and
textures are better preserved by freeze-drying.
Freeze-dried fruits and
vegetables generally have better texture and
rehydration quality. As fresh fruit, salads and
dairy products to be stored safely for longer
periods, particularly during warm weather.

18. Freeze drying of tomato
Freeze drying of fig

19. FREEZING PRESERVATION
• Freezing may preserve foods for long periods of
time provided the quality of the food is good to
begin with and the temperature of storage is far
enough below (-18 ) the actual freezing
temperature of food for long preservation.
IQF or Quick freezing process?
• In this case the lower temperatures (–32 to –
40 ) to freeze foods. The crystals are formed and
the time of freezing is greatly reduced. In quick
freezing, large amount of food can be frozen in a
short period of time

21. The products that can be prepared
from major fruits are:
 Mango: Pulp, canned juice, canned slices, osmotically dried slices,
beverages, fruit bars, jams.
 Grapes: Wine, Raisin, RTS beverage, concentrated beverages, canned
berries.
 Banana: Chips, beverages, clarified juices, mixed fruit jam.
 Pineapple: Canned slices, RTS beverage, concentrated beverages,
canned juice, fruit bars etc.
 Papaya: Tutti-frutti, fruit bar, mixed fruit juices, mixed fruit jam.
 Passion fruit: Concentrated juices, blended juices.
 Butter fruit: Bread spread
 Custard apple: Beverages, mixed fruit jam.
 Guava: Clarified fruit juices, jelly, jam.
 Apple: Juice, jam, fruit bar.

22. PACKAGING MATERIAL
• Packaging materials must be moisture-vapour resistant
• Durable and leak proof
• Not become brittle and crack at low temperatures
• Resistant to oil, grease or water
• Protect foods from absorption of off-flavors or odours
• Easy to seal
• Easy to mark.
Good freezing materials include rigid containers
made of aluminum, glass, plastic, tin or heavily waxed
cardboard; bags and sheets of moisture-vapor resistant
wraps; and laminated papers made especially for freezing.

23. Wooden pallet
Different packing
materials

24. Packing material for fruits and leafy vegetables

25. NET PACKING OF APPLES
Box packing

26. Modified atmospheric packaging
 Modified atmosphere conditions are created inside the
packages by the commodity itself and / or by active modification.
 Commodity – generated or passive MA is evolved as a
consequence of the commodity’s respiration. Active modification
involves creating a slight vacuum inside the package and replacing it
with a desired mixture of gases
 Another active modification technique is the use of carbon dioxide
or ethyl absorbers (scavengers) within the package to prevent the
build-up of the particular gas within the package. This method is
called active packaging. Compounds like hydrated lime, activated
charcoal, magnesium oxide are known to absorb carbon dioxide
while iron powder is known to absorb carbon dioxide. Potassium
permanganate, squakna and phenyl methyl silicone can be used to
absorb ethylene within the packages

27. MAP

28. Controlled Atmospheric
• This refers to a storage atmosphere that is
different from the normal atmosphere in its
composition, wherein the component gases
are precisely adjusted to specific
concentrations and maintained throughout
the storage and distribution of the perishable
foods.

29. OTHER PRODUCTS FROM FRUITS
• Squash
• Jam
• Jelly
• Candy

30. REFERENCES
• http://www.iihr.res.in/faq/FAQ.htm
• http://agridr.in/tnauEAgri/