Activity of Goats' Milk Lactoperoxidase System on Pseudomonas fluorescens and Escherichia coli at Refrigeration Temperatures

Zapico, P.; Gaya, P.; Nuñez, M.; Medina, M.

Bactericidal activity of the lactoperoxidase (LP) system against Pseudomonas fluorescens was observed in refrigerated raw goats' milk. Mean decreases in the levels of P. fluorescens of 1.69 log units at 4°C and 1.85 log units at 8°C were achieved during the first 24 h by LP-system activation. Inhibitory activity depended on temperature and length of incubation. P. fluorescens counts lower than the initial level were recorded in activated LP-system milk for 5 days at 4°C and 3 days at 8°C. Escherichia coli did not grow in raw goats' milk at 4°C, and the influence of LP-system activation at this temperature on E. coli counts was negligible. At 8°C, E. coli was able to grow in control milk with no apparent lag phase. In contrast, a lag phase of 2 days was observed in activated LP-system milk at 8°C, resulting in lower E. coli counts than those of control milk during the first 5 days.