Drying and dehydration of fruits and vegetables

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 .

15. 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.

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

17. 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.

18. Drying Rates

19. 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)

20. 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.

21. 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

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. 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.

24. 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.

25. Ref- https://www.researchgate.net/publication/275650176_Different_Drying_Methods_Their_Applications_and_Recent_Advances 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