Solar Drying Technology for Food Preservation

Food losses in the developing world are thought to be 50% of the fruits and vegetables grown and 25% of harvested food grain (Burden, 1989). Food preservation can reduce wastage of a harvest surplus, allow storage for food shortages, and in some cases facilitate export to high-value markets. Drying is one of the oldest methods of food preservation. Drying makes produce lighter, smaller, and less likely to spoil. This paper presents the background and possibilities of solar drying, focusing on the technical needs of small farmers in the developing world. (The important social and cultural implications of introducing a new technology are not addressed here). The background section explains the moisture content of foods, how moisture is removed, and the energy required for this drying process. The “Solar Drying Essentials” section discusses drier components, the drying process, and the capabilities of solar driers. The paper concludes with a classification of drier types, some criteria for selecting a drier, and references to further information. Background Preserving fruits, vegetables, grains, and meat has been practiced in many parts of the world for thousands of years. Methods of preservation include: canning, freezing, pickling, curing (smoking or salting), and drying. Food spoilage is caused by the action of molds, yeasts, bacteria, and enzymes. The drying process removes enough moisture from food to greatly decrease these destructive effects.