Presentation on theme: "Efficient Drying and Safe Storage of Agricultural Seeds and Products Elizabeth Mitcham University of California, Davis Director, Horticulture CRSP Director,"— Presentation transcript:
Efficient Drying and Safe Storage of Agricultural Seeds and Products Elizabeth Mitcham University of California, Davis Director, Horticulture CRSP Director, 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. Bradford University of California, Davis Rhino Research, CABI, IDE, CEAPRED Horticulture 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 Desiccants Desiccants 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 development Service model could be developed for regeneration of beads for farmers - microenterprise
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 storageAfter 6 mo storage Open stored vs Bead stored All seeds germinate Seedlings Higher seedling vigor
Six months storage Without beads 69% infestation With beads 0% 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 Applications Drying of fresh horticultural products Chili peppers
Drying of Apple and Tomato Slices with Drying Beads Ratio 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