Comportamento de bactérias patogênicas em queijos artesanais de Minas durante a maturação

Abstract

The state of Minas Gerais is the largest cheese producer in Brazil, being recognized for its traditional production of artisanal cheeses. Artisanal cheeses from Minas Gerais have very different characteristics, due to the specificities of the production process, but they have in common the use of raw milk during their preparation. The concern about the consumption of these products occurs due to cases of food poisoning, associated with cheeses contaminated with pathogens, including Listeria monocytogenes. Therefore, understanding microbial development in cheese is important, especially during maturation, since during this period, the intrinsic environment of the cheese may be unfavorable to the establishment and growth of microorganisms. Considering these aspects, the objective of this study was to evaluate microbial behavior, especially inoculated L. Monocytogenes, as a function of pH and water activity (aw) values, obtained throughout the maturation process in artisanal cheeses from Minas Gerais. For this, two types of cheese were collected immediately after salting, coming from the Campos das Vertentes (QMA-CV) and Serra da Mantiqueira (QAM-M) regions. In the laboratory, the samples were inoculated with L. monocytogenes ATCC 19117 (8 log CFU/mL) and stored in a maturation room for 35 days. Separately, samples without inoculation were evaluated, in the same period of time, for the quantification of L. monocytogenes, Salmonella, Escherichia coli, coagulase-positive Staphylococcus, lactic acid bacteria and filamentous fungi and yeasts. Monitoring the viability of microorganisms was carried out using a cultivation-dependent method. All samples were subjected to pH and aw measurements. The results indicated that, under the conditions proposed in this study, the inoculated Listeria monocytogenes population reduced over the maturation time, reaching counts of 3.15 log UFC g-1 and 2.84 log UFC g1 in QAM-M and QMA- CV, respectively. Showing that maturation is efficient in reducing this bacteria. L. monocytogenes and Salmonella sp. were detected in no non-inoculated sample. The QAM-M showed an initial count (before maturation) of coagulase- positive Staphylococcus of 5.63 log CFU g-1 and 3.63 log MPN g-1 of E. coli, however, until the end of maturation, the number of these microorganisms was reduced, remaining within the recommended limits. In uninoculated QMA-CV, coagulase-positive Staphylococcus and E. coli were not detected. Both varieties of cheese showed high total counts of fungi and lactic acid bacteria, as well as a reduction in aw and pH over time.