DESIGN AND PERFORMANCE ASSESSMENT OF A FLAT-PLATE SOLAR MILK PASTEURIZER FOR ARID PASTORAL AREAS OF KENYA

A solar milk pasteurizer consisting of flat-plate water-heating collector and a 1.5-mm thick stainless steel cylindrical milk vat was designed and tested in an arid pastoral area of northern Kenya. The milk vat had a capacity of 80L and a 50-mm wide hot water jacket insulated with 38-mm thick fiberglass. Hot water produced by the collector was used for pasteurizing milk. The optimum quantity of milk that could be pasteurized by this device under the study conditions was 40L, and the average temperature difference between hot water and milk being pasteurized was 8.1 +/- 1.4C. Total bacterial counts in pasteurized milk were less than 10cfu/mL while coliform counts were negative. This low-cost solar milk pasteurizer is appropriate for arid pastoral areas without grid electricity, where milk marketing is an important income source, and where most of the milk is boiled using firewood. PRACTICAL APPLICATIONS Milk marketing is an important income source for people in arid areas of Kenya. To minimize losses along the marketing chain, traders boil milk using firewood, especially when transport to the market is unavailable. This places intense pressure on woody resources on the fragile environment. There is abundant supply of solar energy in the arid areas that can be harnessed using flat-plate solar collectors to provide hot water for milk processing, and thus save on the environment. The hot water produced by the solar pasteurizer could also be used for cleaning milk containers, thus improving hygiene of milk marketing. The study is expected to enhance milk marketing in arid areas, increase food security and encourage wider use of solar energy in food processing in Kenya. On a global scale, use of solar energy would reduce the rate of depletion of fossil fuels and minimize pollution arising from their use.