Solar Food Drying

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SOLAR FOOD DRYING The art of drying food using solar energy is a little more complicated than you might think. We have tried to gather some practical information and to provide links to other resources. Although dried food is popular with campers, backpackers etc. this page is driven by the need for solar dryers in areas where fruit is plentiful in summer months, but because there is no simple and economic method to preserve it, much of it is left to rot, while in the winter there is hunger. Solar food drying can be used in most areas but how quickly the food dries is affected by many variables, especially the amount of sunlight and relative humidity. There are some basic guidelines to drying food. Most of the resources we researched recommend pre-treatment of the food, such as blanching, (boiling/steaming).Many experienced users do not pre-treat food. Wash fresh fruits and ripe vegetables thoroughly. Effective drying is accomplished with a combination of heat and air movement. Remove 80 to 90% of moisture from the food. Typical drying times range from 1 to 3 days, again depending on sun, air movement, humidity, and type of food. Once the drying process has started it should not be interrupted, do not allow to freeze. Direct sunlight is not recommended. Temperature ranges of 100 to 160 degrees will effectively kill bacteria and inactivate enzymes, although temperatures around 110 degrees are recommended for solar dryers. Too much heat especially early in the process will prevent complete drying. Food should be cut into thin slices, less than 1/2" thick and spread out on trays to allow free air movement. Rotate trays 180 degrees daily for uniform drying. Move dryer food to bottom racks. Safe tray materials include Stainless steel rack-wood slats-cheesecloth-Teflon -Teflon coated fiberglass-nylon -food grade plastics Allow food to cool completely before storing. Store food in air tight jars or plastic containers, and do not expose dried food to air, light or moisture. Most fruits taste great dried including apples, apricots bananas, grapes etc. Vegetables are best reconstituted by covering with cold water until they are near original size. They can be added in their dry form to soups/stews. Vegetables can also be ground into powders and used for instant soups or flavoring. RESOURCES http://muextension.missouri.edu/xplor/hesguide/ foodnut/gh1562.htm http://www.cahe.nmsu.edu/pubs/e-322.htm good chart on preparation and drying times. http://www.agen.ufl.edu/~foodsaf/he520.html Abstracts http://www.ariadne-t.gr/phaethon/solar/dryabst/ dryabst.html Proceedings of Ises Solar World Congress Budapest 1993, Volume 8.Numerous papers on solar drying of various crops. Plans From: Home Power Magazine http://www.humboldt1.com/~michael.welch/extras/fooddeh.pdf http://www.uky.edu/Agriculture/Forestry/ AppalFor/tp.html ($2.)

Basic Solar Dryer

 

Interior of box is insulated

Optional solar chimney is glazed on south side and interior is painted black.

 

 

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Last Updated Mar 15, 2007

 

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