Fruits and vegetables can be preserved through canning, freezing, or drying. Canning involves heat processing foods in sealed containers to kill microorganisms. Freezing slows microbial growth and chemical changes by reducing the temperature. Drying removes moisture from foods to prevent spoilage. Selection, washing, peeling or cutting, and appropriate packaging are important preprocessing steps for many preservation methods. Canning, freezing, and drying all aim to preserve the nutritional value and quality of fruits and vegetables for later consumption.

1. Processing of Fruits and
Vegetables
Mohammad Muhaiminul islam
Bsc in Food Engineering
University of Debrecen

2. What is fruit and Vegetable
• Fruits are a high-moisture, generally acidic food that is relatively easy to
process and that offers a variety of flavour, aroma, colour, and texture to
the diet.
• Vegetables consist of a large group of plants consumed as food.
Perishable when fresh but able to be preserved by a number of
processing methods, they are excellent sources of certain minerals and
vitamins and are often the main source of dietary fibre.

3. Methods of Processing:
• Processing of fruits and vegetables is very important to produce
products for direct consumption and as food ingredients.
• There are three major processes,
Canning
Freezing
Dryinng

4. Canning:
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.

5. 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.

6. Principle of canning:
• Destruction of spoilage microorganism within a container
by means of heat.

7. Process
• Selection of fruits and vegetables : Fruits and vegetables should be
absolutely fresh.
• Grading : The selected fruits and vegetables are graded according to
size and colour to obtain uniform quality.
• Washing : It is important to remove pesticide spray residue and dust
from fruits and vegetables.
• 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.

8. • Cutting
• Blanching
• Cooling
• Filling: Before filling, cans are washed with hot water and sterilized
• Sealing within 74°C.
• Processing ( heating)
• Cooling 36°C to 42°C
• Storage

9. Freezing
• Easy, convenient and the least
timeconsuming
• Slows growth of microorganisms and
chemical changes
• Preserves the greatest quantity of nutrients

10. Freezing Overview
• Frozen in many forms – Whole, sliced, crushed, juiced etc.
• Best quality- choose fully ripe, but firm, fruit
– Immature or overripe produce lower quality when frozen
• Types of Packs;
- Syrup pack, Sugar pack, Dry pack, Unsweetened and water packs.
• For vegetable:
- Dry and Tray pack

11. Vegetables: Thawing for Serving
• Most vegetables can be cooked without thawing
• Corn-on-the-cob should be partially thawed before cooking so that it will
heat all the way through
• Leafy greens cook more evenly if partially thawed

12. Storage Times
• Fruits – Most frozen fruits maintain high quality for 8 to 12 months –
Unsweetened fruits lose quality faster than fruits packed in sugar or
sugar syrups
• Vegetables – Most vegetables will maintain high quality for 12 to 18
months at 0°F or lower – Use your home-frozen vegetables before the
next year’s crop is ready for freezing

13. Summary
• Freezing fruits and vegetables is a safe, easy way to preserve foods
• Wash all fruits and vegetables thoroughly
• Follow blanching charts for vegetables
• Use proper procedures and equipment, including freezer-safe
materials
• Use the freezing process that works best for your family meal needs

14. Drying method:
• One of the oldest methods of preserving food
• Alternative to canning & freezing
• Simple, safe and easy to learn
• No refrigeration needed
• Takes little space
• Removes moisture from food so bacteria, yeasts & molds can’t grow
and spoil food
• Slows down action of enzymes but doesn’t inactivate them

15. Factors
• Surface area - The greater the faster the product dries
• Temperature - The greater the difference between the product and
drying medium, the greater the rate of drying
• Humidity - The higher, the slower the drying
• Atmospheric pressure - The lower, the lower the temperature
required to remove water.

16. Binding of Water
• As a product dries, its free
• water is removed
• This water evaporates first .
• Water in colloidal gels, such as starch,
pectin or other gums is more difficult to
remove.
• Water that is most difficult to remove is
that chemically bound in the form of
hydrates

17. Methods of Drying
• Sun drying : in Dry, warm
climates
• Spray drying –
• Tray (air) drying
• Tunnel drying -

18. Packaging requirements for dehydrated foods
• Protect against moisture absorption
Dehydrated foods- hygroscopic
Prevent transmission of water vapor
• Physical protection
Prevents crushing
Freeze dried foods- porous structures with spaces; easily crushed
• Protection from oxygen and light
photo- oxidation

19. Benefits
• Tastes Great
• Less Expensive
• Less Expensive
• Portable
• Reduces Waste
• Flexible & Versatile.
• Efficient Storing.