Isolamento e classificação de micro-organismos psicrotróficos proteolíticos presentes em queijo Minas Frescal / Isolation and classification of psychrotrophic and proteolytic microorganisms in “Minas Frescal” cheese

Algumas condições da qualidade de leite e derivados estão conexas à microbiota contaminante deterioradora que é, sobretudo, representada por bactérias psicrotróficas proteolíticas. Portanto, o objetivo desse trabalho foi isolar micro-organismos psicrotróficos proteolíticos de queijo Minas Frescal comercializados em Salinas -MG. Para tanto foi realizado o isolamento de micro-organismos psicrotróficos proteolíticos presentes em queijos Minas Frescal. Logo após, foi realizada a caracterização dos isolados quanto à coloração de Gram, forma e atividade de oxidase. Os resultados obtidos evidenciaram a predominância de micro-organismos psicrotróficos Gram-positivos na microbiota dos queijos comercializados em Salinas-MG.

Performance of two alternative methods for Listeria detection throughout Serro Minas cheese ripening

ABSTRACT The ability of pathogens to survive cheese ripening is a food-security concern. Therefore, this study aimed to evaluate the performance of two alternative methods of analysis of Listeria during the ripening of artisanal Minas cheese. These methods were tested and compared with the conventional method: Lateral Flow System™, in cheeses produced on laboratory scale using raw milk collected from different farms and inoculated with Listeria innocua; and VIDAS®-LMO, in cheese samples collected from different manufacturers in Serro, Minas Gerais, Brazil. These samples were also characterized in terms of lactic acid bacteria, coliforms and physical-chemical analysis. In the inoculated samples, L. innocua was detected by Lateral Flow System™ method with 33% false-negative and 68% accuracy results. L. innocua was only detected in the inoculated samples by the conventional method at 60-days of cheese ripening. L. monocytogenes was not detected by the conventional and the VIDAS®-LMO methods in cheese samples collected from different manufacturers, which impairs evaluating the performance of this alternative method. We concluded that the conventional method provided a better recovery of L. innocua throughout cheese ripening, being able to detect L. innocua at 60-day, aging period which is required by the current legislation.