Determinacion de crecimiento y sobrevivencia de Escherichia coli O157:H7 y Salmonella typhimurium en la elaboracion del queso de hoja (Spanish text)

The survival of Escherichia coli O157:H7 and Salmonella typhimurium during the processing steps of “queso de hoja” was determined. In this study, both pathogens were inoculated, separately, into raw cow's milk. “Queso de hoja” was made from this milk and the survival of these two bacteria was determined in each of several steps during the manufacturing process. Escherichia coli O157:H7 was isolated through the process up to the fermentation step. This pathogen did not survive the steps of heat treatment (85–95°C) with addition of salt (2.76%) to the fermented curd and was not detected in the final product. Salmonella typhimurium survived through all the steps of the manufacturing process and was found in the final product. Chemical analysis of inoculated and noninoculated “queso de hoja” determined its composition: 43.69% humidity; 0.98 water activity (Aw); 7.44% ash; 0.81% sodium chloride; 26.09% protein; 23.35% fat and 4.98 pH.