Abstract:
For this research a problem was identified for the small scale pasteurizing of milk in rural areas of
the Free State. The sun was utilized as an energy source for the pasteurizing process. Several
experiments were carried out with existing solar panels but it was unable to reach the desired
water temperature of 65°C. Tests were also conducted to get the ratio between the area, the
volume of water in the tank and the volume of the milk that could be pasteurized in one batch.
The solar panel that was developed, consisted of a double bank flat copper tubes of 0,6 m2 area
that could heat up 13 liter of water to the desired temperature in approximately 3 hours. The milk,
sealed in one litre plastic bags, could then be put into the tank for the pasteurizing process. A
mirror of 0,3 m2 area underneath the copper tubes reflects the sunbeams for more effective
heating of the water. A mirror on the side of the panel was used to regulate the heat to the water if
the desired temperature was exceeded. This milk pasteuriser has the capacity to pasteurize 1 litre
of milk in approximately 71 minutes.
The milk was tested at the University of the Orange Free State and the results indicated that the
milk so pasteurized complied 100 % to the requirements.
This research make it now possible to pasteurize milk very economically by utilizing solar energy,
to the benefit of the small scale farmer in rural areas.
