Supervivencia de listeria monocytogenes en queso bajo diferentes condiciones de almacenamiento

Abstract

Raw sheep milk cured cheese is catalogued as ready-to-eat since it is not submitted to any further treatment before consumption. Thus, foodborne pathogens such as Listeria monocytogenes can represent a health concern for susceptible consumers. The tolerance of this bacterium to cold and its ability to grow at refrigerator temperatures is one of the main security problems for the food industry. This study was aimed at evaluating the survival of L. monocytogenes on raw sheep milk cured cheese under different storage temperatures. Shoulder and Weibull type models were fitted to data observed in order to estimate kinetic parameters. The Arrhenius relationship was further used to predict the impact of temperature on L. monocytogenes behavior during storage at 4, 12 and 22° C. Additionally, growth of lactic acid bacteria (LAB) as a representative group of the indigenous microbiota was evaluated. Results obtained indicated that the time to eradication (time when absence of L.monocytogenes in the analyzed samples was observed) was 114, 104, and 77 days for cheese samples stored at 4, 12 and 22°C, respectively. The LAB population showed an increase at 12 and 22 °C during storage. However, an increase of 1 log CFU/g was observed during the first 2 weeks irrespectively of the storage temperature. The Shoulder model indicated a good fit to observed data. Likewise, the Arrhenius relationship explained sufficiently the dependency of temperature on L. monocytogenes behavior. This study demonstrated that cheese storage at ambient temperatures could lead to the preservation of its quality properties as well as its safety against L. monocytogenes.