Microbiological Characteristics and Behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Staphylococcal Toxin during Making and Maturing Cotija Cheese

María de los Ángeles Olea-Rodríguez,Javier Castro-Rosas,Olga Vázquez-Paulino,Ma. Refugio Torres-Vitela,Angélica Villarruel-López,Karla Nuño,Patricia Chombo-Morales,Luz E. Garay-Martínez,Zuamí Villagrán-de la Mora

doi:10.3390/app11178154

María de los Ángeles Olea-Rodríguez, Javier Castro-Rosas + Show 7 more

Open Access

https://doi.org/10.3390/app11178154

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Abstract

Cotija cheese is an artisanal matured Mexican cheese from unpasteurized milk. This work determined the microbiological characteristics and behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and staphylococcal toxin during cheese elaboration and ripening. Sixteen 20-kg cheeses were used, eight inoculated with 6 log CFU/mL of each pathogen, and eight uninoculated, and samples were taken at each stage of the process. In the uninoculated samples, the survival of S. aureus and L. monocytogenes decreased after 30 days of ripening. The average counts of S. aureus in milk, curd, and serum were 7 log MPN /mL, and 8.7 log MPN /g in cheese, decreasing from day 15. Salmonella spp. counts (initial inoculum: 7.2 log MPN /mL) decreased after 24 h, and L. monocytogenes counts (8.7 log MPN/g at 24 h) decreased from day 15 in the cheese. Salmonella spp. and L. monocytogenes were not detected in any sample after 60 days of ripening, unlike S. aureus, which was detected at the end of the study. Lactic acid bacteria counts were 9 log CFU/mL in milk and whey and 7.2 log CFU/g in cheese. Pathogens behavior during the ripening process reduces the health risks by consuming products made with unpasteurized milk when subjected to ripening.

Highlights

In the case of Cotija cheese, it is a Mexican artisan product made from raw cow milk without any heat treatment
There was a space to work with inoculated milk, and the cheeses were stored for 90 days for their maturation, such as the traditional process of Cotija cheesemaking
Strains used in inoculated cheese were typified: Staphylococcus aureus ATCC 13565, Salmonella Typhimurium ATCC 14028 and Listeria monocytogenes ATCC BAA-751

Summary

Introduction

In Mexico, most fresh cheeses are handmade using rustic methods in micro-industries located in small cities. These industries generally have little or no quality control and high composition and sensory parameters variability, leading to a limited shelf life [2,3,4]. Interaction within the milk microbiota is vital for the characteristics of the final product. It participates from the acidification of the curd to the formation of compounds that determine the aroma, flavor, and texture during ripening [8,9]. The diversity of the native microbiota contributes to the final sensory properties and biopreservation [10,11]

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