The rearing of Serrano handmade cheese aims to reduce populations of pathogenic and deteriorating microorganisms since the dairy product is not pasteurized. To ensure the quality and safety of the product, it is possible to establish mathematical models for the inactivation of pathogens and determine the optimal cheese ripening time.
Handmade cheeses are seen by consumers as natural foods, for which traditions and origins are valued characteristics. In some states of Brazil, handmade cheese is produced from raw milk from cattle, through production processes peculiar to each region, representing expressive potential for the local economy.
Maturation is the final stage of the process of manufacturing handmade cheeses and can last up to 60 days. During this period, biochemical transformations occur in cheeses, with a sharp reduction in moisture and pH, and an increase in sodium chloride concentration - conditions that contribute to the control of the growth of undesirable bacteria and for the development of beneficial microorganisms, responsible for the texture and taste characteristic of cheeses (Leclercq -Perlat et al., 2015; Callon et al., 2016).
The absence of thermal treatment of milk in the process, however, makes the production of handmade cheese heavily dependent on good manufacturing practices, as well as ripening, in dealing with pathogenic and deteriorating microorganisms. However, such care is not always sufficient.
With the aim of establishing mathematical models for the inactivation of pathogens and, in accordance with the Brazilian Regulatory Norms, to determine the optimal ripening time for handmade cheese produced in Campos de Cima da Serra, RS, researchers from the State University of Rio Grande do Sul developed the research Modelagem cinética de inativação de bactérias patogênicas em queijo artesanal serrano durante a maturação. The study was published in volume 24 of the Brazilian Journal of Food Science and Technology.
The research encompassed the handmade serranos cheeses obtained in family agro-industries, controlled and legalized, in the city of São Francisco de Paula (RS, Brazil), produced between September 2016 and March 2017, with an average mass of 500 g.
Data on the inactivation of bacteria of food origin were evaluated during the ripening of the samples collected. The results showed the absence of Salmonella spp. and L. monocytogenes throughout the ripening period, by the Brazilian Regulatory Standards. The population data for fecal coliforms and S. aureus were then adjusted to the first-order, log-linear + shoulder, and Weibull models. The log-linear + shoulder model did not present satisfactory results, and Table 1 shows the statistical parameters of the adjustments of the other mathematical equations.
Analysis of mathematical modeling showed that serranos cheeses should be ripened for at least 33 days, based on fecal coliforms and the positive coagulase strain of S. aureus. The results are in accordance with other works that point to a minimum period of 30 days of ripening for serrano handmade cheeses to develop the appropriate sensory characteristics as well as for microbiological stabilization.
In the opinion of the researchers, knowledge of bacterial inactivation kinetics is an important tool in ensuring the food safety of handmade cheeses. The study showed that mathematical models, which are a concise way of expressing physical behavior, have enabled us to establish more accurately the maturity period of handmade serrano cheeses, contributing to compliance with the legislation and to the marketing of a product that is safe from the point of view of public health.