Brief information on drying and dehydration of fruits and vegetables to enhance self life of it.

1. Drying and Dehydration of fruits and vegetables

2. COLLEGE OF HORTICULTURE
An Assignment Presentation
On
“Drying and Dehydration of fruits and vegetables ”
Course No.: HWE- 7.3 (POST HARVEST HANDLING AND VALUE
ADDITION IN HORTICULTURE CROPS)
Present to:-
Mr. Alok Nath
College of Horticulture
S.D. Agricultural University,
Jagudan, 382710
Presented by:
Name : Shubham Kumar

3. Difference Between Drying and
Dehydration-
Both the terms ‘drying’ and ‘dehydration’ mean
the removal of water. But the former term is
generally used for drying under the influence of
non-conventional energy sources like sun and
wind whereas dehydration means the process of
removal of moisture by the application of
artificial heat under controlled conditions of
temperature, humidity and air flow.

4. Drying (Dehydration)
 One of the oldest methods of
preserving food.
 Removes moisture stops the growth
of bacteria, yeasts & molds that
normally spoil food.
Slows down but doesn’t completely
inactivate enzymes.

5. Benefits of drying-
Fruits and vegetables are dried to enhance
storage stability, minimize packaging requirement
and reduce transport weight.
Preservation of fruits and vegetables through
drying based on sun and solar drying techniques
which cause poor quality and product
contamination.
An optimum drying system for the preparation of
quality dehydrated products is cost effective as it
shortens the drying time and cause minimum
damage to the product.

6. Fruits and Vegetables suitable for drying-

7. Drying Techniques
• Sun or solar drying
• Freeze drying
• Drum drying
• Spray drying
• Foam mat and vacuum belt
• Convection air & Superheated steam
• Osmotic drying
• Microwave

8. Drying Techniques (continued)
• Combination of different techniques
• Vacuum- osmotic
• Osmotic – microwave
• Ultrasound pre-treatment
• Fluidized bed
• Pulse combustion
• Jet zone or impingement

9. Sun Drying
Fruits safe to dry due to high acid and
sugar content.
 Vegetables should not be dried outside
• They need constant temperature &
airflow.
Temperature of 30 C or higher for
several days with humidity below 60%
Cover to protect against insects/pests.

10. Sun Drying of fruits and vegetables

11. Solar Drying
Need to construct a dryer with panel(s).
Need to stir and turn food several times a
day.
Need several days of sun in a row.

12. Freeze drying
Freeze-drying, also known as lyophilisation,
or cryodesiccation, is a dehydration process
typically used to preserve a perishable material
or make the material more convenient for
transport.
Freeze-drying works by freezing the material
and then reducing the surrounding pressure to
allow the frozen water in the material to
sublimate directly from the solid phase to the
gas phase.

13. Freeze dryer

14. Oven drying
By combining the factors of heat, low humidity
and air flow, an oven can be used as a dehydrator.
Oven drying is slower than dehydrators because
it does not have a built-in fan for the air movement.
It takes about two times longer to dry
food in an oven than it does in a dehydrator.
Thus, the oven is not as efficient as a dehydrator
and uses more energy.

16. Room Temperature Drying
Method used mainly for herbs & hot
peppers
»Strung on string or tied in bundles and
suspended from overhead racks in air until
dry.
»Enclosed in paper bags with openings for
air circulation.
»Herbs can also be dried in the microwave
oven.

17. •Room drying by
suspension on string
•Drying by folding
in towel or paper

18. Temperature for Drying
The ideal temperature for drying or
dehydrating foods is 60-70 C.
If higher temperatures are used, food
cooks instead of dries
Avoid “case hardening” – dried on outside
but moisture trapped inside allowing mold
growth.
Temperature close to glass transition gives
better products.

19. Drying Rates

20. Factors affecting drying
• Temperature
• Humidity
• Air velocity
• Direction of air flow
• Type of dryer
• Type and size of food (very difficult to
remove last 2% of moisture)

21. The Process
• Prepare the fruit: wash,
core and peel if desired
• Fruits can be halved or
sliced and some left whole
• Thin, uniform, peeled
slices dry fastest
• If fruit is whole, “check”
or crack the skin to speed
drying.

22. Pre-treatment
Some fruits need to have their enzymes
inactivated before drying, especially those
that oxidize when exposed to air (e.g.
bananas, apples, pears)
• Ascorbic Acid
• Fruit juice dip
• Honey dip
• Syrup blanching
• Commercial acids

23. Pre-treatment
Some fruits need to have their enzymes
inactivated before drying, especially those
that oxidize when exposed to air (e.g.
bananas, apples, pears)
• Ascorbic Acid
• Fruit juice dip
• Honey dip
• Syrup blanching
• Commercial acids

24. Future prospects and needs-
There is a large amount of research, and
available knowledge, carried out by academia,
but the industry is not taking full advantages
even in the more developed countries.
A lack of interaction between researchers
and industry is observed worldwide, as a
consequence industrial advancement is slow
because there is a mismatch between research
and industrial needs.

25. Conclusions-
Advances in dehydration techniques and
development of novel drying methods have in recent
years enabled the preparation of a wide range of
dehydrated products and convenience foods from fruits
and vegetables meeting the quality, stability and
functional requirements coupled with economy.
This has been made possible by the sustained
experimental studies over the years to understand the
theoretical and fundamental aspects of the process and
optimization of the techniques to achieve a favourable
combination of cost and quality.

26. Ref-
https://www.researchgate.net/publication/275650176_Differe
nt_Drying_Methods_Their_Applications_and_Recent_Advance
s
http://www.aginnovation.org/wp-
content/themes/theme/images/Drying%20and%20Dehydration
%20of%20Fruits%20and%20Vegetables.pdf
http://www.aginnovation.org/wp-
content/themes/theme/images/Drying%20and%20Dehydration
%20of%20Fruits%20and%20Vegetables.pdf