[Effect of in-home boiling and refrigeration on bacterial load of pasteurized milk] / Efeito da fervura doméstica e da refrigeração na carga bacteriana do leite pasteurizado tipo C.

ABSTRACT

OBJECTIVES: To assess the efficacy of in-home boiling of pasteurized milk in reducing the bacterial load and the ability of the refrigeration in preserving the milk after boiling.METHODS: Thirty samples of pasteurized milk bought in São Paulo, Brazil, were submitted to in-home boiling procedure at the laboratory. Portions of samples were taken before and after boiling, and after 2, 4, 6 and 24 hours under refrigeration for microbiological analyses. Methods used were mesophilic bacteria count, and coliforms and Escherichia coli (E.coli) enumeration.RESULTS: No sample presented mesophilic bacteria count above the Brazilian standard for pasteurized milk. E.coli was not recovered from any sample. Ten samples (33%) had coliform bacteria; of these, 3 samples (10%) were above the standard. Mesophilic bacteria count after boiling was significantly lower than before boiling. After 24 hours under refrigeration, mesophilic bacteria count was significantly higher than after boiling. No significant differences were found between the intervals of 2, 4, 6 and 24 hours under refrigeration. Samples before boiling presented significantly higher coliform bacteria. No coliform bacteria were recovered at any time after boiling.CONCLUSIONS: In-home boiling of milk reduced bacterial load, while refrigeration kept bacteria under low counts.