Queijo Minas artesanal da Canastra: inocuidade e transformações durante a maturação

Abstract

The Minas Artisanal Cheese (MAC) is a characteristic product of the state of Minas Gerais, Brazil. It is produced with raw cow's milk and the addition of an endogenous starter culture called "pingo", responsible for the inoculation of specific microorganisms that can enhance the taste and sensory aspects. The high economic and cultural importance of artisan cheese in Brazil justifies the efforts to guarantee its safety, quality and origin. Thus, the present work aimed to: i) Evaluate the physical-chemical relationship and microbial dynamics during ripening of artisanal minas cheese produced in different farms, by molecular, physical-chemical and multivariate methodologies. ii) Study the process of artisanal minas cheese safety by inoculation of foodborne pathogens during the thirty-day ripening process, using chemical, molecular tools and multivariate statistical analysis. For this purpose, freshly made artisan Minas cheeses from the Canastra microregion (MAC-CM) were collected from farms located in Bambuí and Tapiraí. A study of microbial dynamics was performed by culture dependent methodologies, by the use of differential selective media, and culture independent methods, the PCR-DGGE. Furthermore, Staphylococcus aureus ATCC13565 and Listeria monocytogenes ATCC 19117 were isolated and qPCR methodology was used to follow the sea and hlyA gene expression, respectively. To evaluate the physiology of maturation, liquid chromatography (HPLC) techniques were employed for organic acids and carbohydrates, gas chromatography (GC), for volatile compounds, and Fourier transform infrared spectroscopy (FTIR). The use of artificial neural networks (ANN) and self-organizing maps (SOM) were used to understand the ripening process, as well as to evaluate the relationship of the parameters. In the first topic evaluated in this work, the cheeses produced in different cheese farms, presented different regarding the microbial consortium, directly influencing the ripening process. In general, the lactic acid bacteria (LAB) were linked to the production of basic compounds, such as organic acids, and the mesophilic aerobes, yeasts and filamentous fungi (when present), were connected with the production of volatile compounds and to processes such as proteolysis, mainly. Regarding the second objective, the reduction of the population of pathogenic microorganisms inoculated along the maturation time was observed, mainly by the action of BAL and filamentous fungi. Nevertheless, the quality of these cheeses at the end of ripening demonstrated that thirty days is not enough to eliminate these microorganisms from the products, only to decrease the risk of contamination of the consumer. Thus, there is a need to correlate the good manufacturing practices to the production chain of Minas artisanal cheese to ensure the quality of the ripened cheese.