Efficient Drying and Safe Storage of Agricultural Seeds and Products
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Transcript of Efficient Drying and Safe Storage of Agricultural Seeds and Products
Efficient Drying and Safe Storage of Agricultural Seeds and Products
Elizabeth MitchamUniversity of California, Davis
Director, Horticulture CRSPDirector, Postharvest Technology Center
Seed Quality Is Essential for Agricultural Productivity
Two key components of seed quality:• Improved varieties • High viability and germination capacity
– Produce high quality seed– Store seeds with minimal loss of viability until
needed
Zeolite Drying Beads for the Seed Industry
Peetambar Dahal and Kent J. BradfordUniversity of California, Davis
Rhino Research, CABI, IDE, CEAPREDHorticulture CRSP
Novel seed drying beads based on zeolites (molecular sieves) make it feasible to efficiently dry and store seeds at low RH.
High Relative Humidity Shortens Seed Storage Life
Seeds are very sensitive to the ambient relative humidity (RH) of the air.
Seed storage life is dramatically reduced at high relative humidity.
Humid Conditions in Tropical Regions Cause Rapid Loss of Seed Viability
Ambient conditions in tropical regions often exceed 75% RH and 30°C during the monsoon season following seed harvest, resulting in rapid seed deterioration in open storage.
Traditional Drying Methods Cannot Reduce Seed Moisture Sufficiently under Humid Conditions
Seeds equilibrate with air humidity. Air drying cannot reduce seed moisture content to safe storage levels in humid climates.
Alternative: Drying with DesiccantsDesiccants can be used to absorb moisture from seeds.
Current desiccants have drawbacks that have prevented their widespread use for seed drying and storage.
Novel seed drying beads based on zeolites (molecular sieves) make it feasible to efficiently dry and store seeds at low RH.
Advantages of Desiccant Drying Beads
• Drying Beads can dry seeds to a specific and low MC at ambient temperatures in moisture-proof containers
• Dry seeds inside moisture-proof containers are also protected from molds, insects and rodents
• Seed quality is preserved for several years• No need for cold storage to maintain seed viability
– Even for seed banks
Costs of Zeolite Desiccant Beads
• 0.3-0.5 beads to seeds ratio for one-step drying• $10 to $20 per kilogram
– 100kg seed = 30 kg beads = $300 investment• Less beads needed if initial drying by air first• Dries to low moisture content within few days• Beads can be regenerated by heating to high
temperatures up to 10,000 times• Moisture-proof container needed
Regeneration of Drying Beads
Various ways to achieve high temperatures needed for regeneration of beads• Electric oven• Microwave• Wood fire and other energy
sources• Simple device under
developmentService model could be developed for regeneration of beads for farmers -microenterprise
Dry and Store Seeds using Beads
Roberts EH (1972). Viability of Seeds. Chapman and Hall Ltd., Syracuse, NY, pp 14-58.
Other Storage Problems Are Prevented at Low RH
Pepper Seed Storage in Thailand Before storage After 6 mo storage
Open storedvs
Bead stored
All seeds germinate
Seedlings
Higher seedling vigor
Six months storageWithout beads69% infestation
With beads0% infestation
Storage Insect Control using Drying Beads
Courtesy of Keshavulu Kunusoth, ANGRAU, Hyderabad, India
Open-air drying: reduction of 17% in 72 h
Drying beads: reduction of 58% in 72 h
Other Postharvest ApplicationsDrying of fresh horticultural products
Chili peppers
Drying of Apple and Tomato Slices with Drying BeadsRatio 1:8
Stack Dryer• 2 meter stack to increase air flow• Build on earthen berm to maintain heat in evening• Air flow concentrated around drying product• Cheaper to build than standard cabinet dryer• Holds more product• Dried sliced tomatoes in less than half the time (2
days)• Finalist in international competition for drying
breadfruit• Could be used for drying many products, including
grains and seed
Cabinet Dryer
Improved Solar Drying
Thank You!!
http//:hortcrsp.ucdavis.edu