Changes in Bacteriological Quality of Raw Milk Stabilized by Activation of its Lactoperoxidase System and Stored at Different Temperatures

Abstract

Preservation of the quality of raw milk by activation of its natural lactoperoxidase (LP) system was studied. The milk was stored at 4, 10 and 17°C for a total period of 104, 72 and 48 h, respectively. At 4°C, the LP system was activated after 48 and 96 h. At the higher storage temperatures, activation was carried out initially and after 24 h and (at 10°C) 48 h of storage. The results show that, at 4°C, the Standard Plate Count in LP-activated milk remained fairly unchanged for at least 104 h, whereas bacterial multiplication in the controls started after 48 h. At 10°C, an activation resulted in a lag-phase of at least 72 h, but at 17°C this was reduced to below 24 h. The observed changes in the counts of coliforms and psychrotrophs followed the same general pattern. These results suggest that activation of the LP system in combination with moderate cooling (e.g., with available well water) could be a useful alternative to extend the keeping quality of raw milk. Overnight storage might then be possible, provided the initial hygienic quality of the milk is good and the milk is promptly taken care of in the morning.