Effects of Activated Lactoperoxidase System on Microbiological Quality of Raw Milk

The poor microbiological quality of raw cow milk in Turkey is a major concern. It has been speculated that less activation of naturally present lactoperoxidase system in the milk is the reason for its poor microbiological quality. Hence, the objective of this study was to investigate the effects of activation of the lactoperoxidase (LP) system on microbiological quality of the raw milk. The milk samples collected from a dairy farm were analyzed in the laboratory by dividing into two equal parts as activated (experimental) and control group. The experimental group was activated by treatment with equal concentration of sodium thiocyanate and hydrogen peroxide (20: 20 mg/kg) whereas the control sample remained unactivated. All samples were stored at 4 degrees C during 12 h. The microbial load in all the samples was quantitatively determined at 0, 3, 6, 9 and 12 h. The quantitative changes in each microbial species in both growth were recorded and statistically analyzed. The initial count of total mesophilic aerobic bacteria, psychrotroph bacteria, Pseudomonas spp., Enterobacteriaceae and yeast number were 7.10, 5.14, 6.42, 5.93 and 4.31 log cfu/mL, respectively, and at the end of 3 h the counts were 0.43, 2.23, 1.09, 0.93 and 0.37 log cfu/mL, respectively, were lower than controls. Significant (P<0.05) differences were observed for microbial count of activated and control samples except in case of lactic acid bacteria. The results of this study indicate that the addition of thiocyanate and hydrogen peroxidase to the milk activated lactoperoxidase enzyme already present in the milk and slowed down the microbiological growth, especially of the reducing proteolytic Pseudomonas spp. On comparison, the results for total mesophilic aerobic bacteria, psychrotroph bacteria, Pseudomonas spp., Enterobacteriaceae and yeast were statistically significant (P<0.05) and no significant change was observed in case of lactic acid bacteria.