Milk as it emerges from a healthy udder contains very few bacteria and in addition the natural inhibitory systems in milk prevent significant rises in counts for the first 3 or 4 hours at ambient temperatures.
Cooling within this period to 4 oC, maintains the original quality of milk and this is the method of choice for ensuring good quality milk for processing and consumption. This approach is not always feasible in developing countries and a number of options have to be considered to lower temperature and/or retard growth of spoilage organisms.
Partial immersion of milk containers in streams may be an option in some mountainous areas. Evaporative cooling by placing a moist cloth over the metal milk container may also help to reduce temperature. Solar powered cooling systems and charcoal coolers, using evaporation from porous charcoal in an outer ring surrounding the milk container, have met with limited success.
FAO has successfully promoted the adoption of the Codex approved, Lactoperoxidase System(LP-s), based on activation of the natural inhibitory mechanisms in milk using minute quantities of H2O2 and thiocyanate under supervised conditions at collection centres. Details of this procedure are given in LPS