Activation of the lactoperoxidase system as a method of preserving raw milk in areas without cooling facilities

Abstract

Milk spoilage is a major problem to the dairy sector of tropical countries. High temperatures hasten spoilage, which is worsened by the absence of cooling facilities and adequate transportation means. Some chemicals have been tried as milk preservatives in rural areas, but are now forbidden due to toxicological reasons. The use of the lactoperoxidase system (LPS) might offer a solution to milk preservation in such areas. The lactoperoxidase system is a natural antibiotic system in milk, which could be activated to boost its effectiveness. This study focused on the effects of the lactoperoxidase system on raw bovine milk produced in the Western Highlands of Cameroon during the rainy season. Milk was collected from 17 - 31 farmers in Santa village, bulked and activated with thiocyanate and peroxide. The LPS was activated by addition of 10 ppm thiocyanate and 8.5 ppm peroxide to milk, followed by thorough mixing. Part of the milk was left untreated (control). Treated and control samples were kept under three storage conditions: ambient temperature (22 – 25oC), water bath (20^oC) and refrigeration (6 – 8^oC). Samples were monitored for spoilage at hourly intervals, except for those in the refrigerator, which were monitored after every 6 hours. Microbial population was also estimated at intervals, using the standard plate count method. The average increase in shelf life of treated milk with respect to the control milk was +7.1 (SD 2.4) hours under ambient temperatures, +8.1 (SD 3.0) hours in a water bath and +46.2 (SD 21.2) hours in the refrigerator. The LPS limited the activity of lactic acid bacteria, which cause spoilage in milk. Treatment reduced the lactic acid content in milk by 29% under ambient temperature and 15% in water bath after 16 hours. The LPS reduced the microbial load in milk stored under ambient temperature by more than one log cycle, after 8 hours of storage. Treated evening milk could remain in good condition for the next day's use without refrigeration. Therefore LPS treatment can improve on income generation from dairying as it enables farmers sell milk in far-off markets.

Key Words: Lactoperoxidase system, raw milk, preservation