Abstract

Research was conducted from January to April 1998 in the "Centro Acopio Lechero Mune Alto", in Pitrufquén, Region IX, in Chile. The objectives of the study was to evaluate the effect of an activator of a Lacto-peroxidase System (composed of 700 mg of sodium thiocyanate and 1.7 gr of sodium percarbonate) on bacteria growing in milk obtained during the summertime from small dairy farmers. The activation of the Lacto-peroxidase System was measured in milk conserved at room temperature during 12-15 hrs. in summertime. The Lacto-peroxidase System was evaluated after 8 hours under the hygienic conditions stipulated by the Chilean milk industry. 100 lt. of fresh milk were homogenized and divided in two milk containers (50 lt. each). The activator of Lacto-peroxidase System (LPS) was incorporated in one container (treated milk = LT) and the other container was the control (control milk = LC). This procedure was repeated nine times. A second trial was conducted to evaluate the effect of the reactivation of the LPS. 150 lt. of fresh milk was placed into three milk containers; the control (LC) without activator LPS; a container in which LPS (LT1) activator was added; and a third container with LPS activator plus a second dose of sodium percarbonate eight hours after (LT2). Milk samples were obtained at different intervals from all the containers for analysis of bacterial count, presence of inhibitors and peroxide levels. Results show statistical differences (P<0.05) in the enhancement of bacterial counts between LC y LT after 12 hrs of storage, with increments in the function of basal value of 69.4 and 22.5 times respectively. The reactivation of LPS does not show significant differences (P>0.05) at 15 hrs of storage between LT1 and LT2 in bacterial concentration, however, both were significantly lower (P<0.05) compared with LC. Inhibitors and peroxides were not detected in either experiments. The use of the LP system activator was not detected in common tests applied by the milk industry for the detection of inhibitors and peroxides, and for this reason it cannot be considered as a adulterating agent in milk. The conclusion is that even the LP system activator inhibits the micro-bacterial growth, it is not sufficient in order to reach quality standards required in the country.