A new solar-powered milk cooling system could benefit small-scale dairy farmers

Researchers from the University of Hohenheim studied a solar milk cooling system which was tested in Tunisia and could be implemented in Kenya.

In an article1 published in the International Journal of Refrigeration in June 2018, a team of researchers from the University of Hohenheim focused on different ways to cool milk, especially in small dairy farms in African countries.

In these countries, the lack of cooling systems often results in high microbial contamination in a very short time (bacteria levels can exceed the maximum allowed by food safety after 2-5 hours). When the temperature of the milk is reduced from 37°C to 20°C, 10°C or 4°C, the bacterial growth can be partially inhibited for, respectively, the first 8, 16 or 24 hours after milking.

Different methods of cooling have been used in these countries over the years: evaporative cooling, absorption (often powered by solar energy), and vapor-compression cooling.

This last system is explored in this article. It uses ice as a cooling medium, stored in insulated milk cans and provided using a small scale solar system consisting of a commercially available direct current refrigerator powered by photovoltaic panels and batteries. This system has been tested in seven dairy farms of Tunisia from July 2015 to December 2017. The results of the study showed "the ability of the system to cool 30?L milk to 17°C in less than 90 minutes with 6?kg ice. By using the same milk-can with 20?L and 8?kg ice, milk remains below 13°C for over 12 hours at an ambient temperature over 35°C. Even though the storage temperatures used are higher than the 6°C recommended by the European regulation (853/2004), cooling temperatures below 20°C and 15°C are low enough to prevent bacteria growth for 6 hours and 12 hours, respectively".

Thanks to a partnership between the Kenyan company Davis & Shirtliff and the University of Hohenheim, supported by the German International Cooperation Agency (GIZ), small-scale dairy farmers from Western Kenya could benefit from this new solar-powered milk cooling system.

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1 TORRES-TOLEDO Victor. HACK Alice. MRABET Farah. On-farm milk cooling solution based on insulated cans with integrated ice compartment. International Journal of Refrigeration. 2018, vol. 90, 10 p. Available in Fridoc.