Sweet potato has been described in many communities especially those in dry areas as the ‘king of crops’ because of its ever increasing demand. The most favourite drought resistant, hardy crops grow mostly in marginal areas, thus contributing to improved food security and additional income to farmers.
The young leaves and vines are usually consumed as vegetables or fed to livestock.
The orange-fleshed sweet potato variety has high beta-carotene content, which boosts the immune system. Unfortunately, during bumper harvests; farmers often sell sweet potatoes at throwaway prices. Losses after harvesting are high because the tubers are delicate and highly perishable.
In some communities in Eastern Africa, sweet potatoes are preserved for the dry season by sun-drying to make dried sweet potato chips. The dried chips are boiled and mashed with beans, milled or pounded to make flour, which can be mixed with either millet or cassava flours to make stiff porridge.
Some facts about dried sweet potato chips and flour
• Any sweet potato variety can be dried to make chips, which can then be milled into flour.
• Dried sweet potato chips can be stored for up to six months when packaged in airtight, strong, black plastic bags.
• Sweet potato flour can be used to make doughnuts and pancakes.
• Flour made from the chips can also be used to make highvalue flours by mixing with millet, maize or soybean flour. These mixed flours are used to make porridge and baby foods, which are easily digestible.
• Some bakeries are already using new flour mixes to make bread and cakes.
• The poultry feed industry is showing interest in using orange-fleshed chips in their feeds to improve yolk colour and vitamin A content of eggs.
Requirements for making sweet potato chips and flour
• Mature sweet potato roots on average, 4kg of fresh sweet potato roots which will give about 1 kg of dried sweet potato chips.
• A clean area, ideally a room with raised working surfaces, such as tables – not on the ground.
• Large plastic containers, preferably 10 to 20 litre buckets with lids.
• Supply of clean water.
• A manual or motorized sweet potato chipper for chipping or slicing.
• Raised open platform for air drying, or ideally a solar dryer, placed in a clean area in full sun.
How to make sweet potato chips and flour
Step 1: Choosing the roots
• Use any sweet potato variety.
• The tubers should be undamaged and mature – three to four months for the early maturing varieties and five to six months for the late maturing varieties.
Step 2: Washing
• Wash the sweet potatoes in clean water in large buckets, changing water as frequently as required.
• Alternatively, you can wash the roots in a sweet potato drum washer when processing large quantities to speed up the process.
• Do not peel the roots because the peel is rich in nutrients.
Step 3: Draining
• After washing, drain by placing the sweet potatoes on a raised, perforated rack.
Step 4: Chipping or slicing
• Chip the washed sweet potatoes to uniform size (3-6 mm thick).
• You can slice them manually with a sharp knife or use a manual or motorized chipper to speed-up the process.
Step 5: Drying
• Sweet potato chips should be evenly spread on a raised platform, preferably on a clean, black plastic sheet, to sundry under maximum sunshine for about six to eight hours – it is best to do this during the hot, dry season.
• To ensure high quality chips, solar dryers can be used. A modified solar dryer, called a hybrid solar dryer, which has an additional energy source, such as charcoal, and can be used to dry the chips. Information on availability of fabricators of chippers and solar dryers can be obtained from your local extension officer or national agricultural research station.
• Chips should be dried until they are brittle.
• If drying in the open, cover chips with netting to keep off insects and birds.
• Pack chips or continue processing to flour.
Step 6: Milling
• Mill dried chips to flour using the ordinary posho mill.
Step 7: Packaging and labelling
• Pack dried chips or flour in strong (thick gauge) black polyethylene bags. Flour can be packaged in 2kg packs for distribution to shops and other retail outlets.
• Label product to state source, date of manufacture and expiry date (after six months).
• Place bags of dried chips or flour in cardboard cartons to protect them from light.
Step 8: Storing
• Store in a cool, dry place off the ground, preferably on pallets or raised surfaces.
• Flour can be stored for six months.