Modeling the effects of ripening at refrigeration and ambient temperatures on physic-chemical and microbiological parameters of artisanal Minas cheese

Abstract

This study aimed to assess the effects of ripening at refrigeration and ambient temperatures on physic-chemical and microbiological parameters of artisanal Minas cheeses (made from raw milk) and to model the kinetics of lactic acid bacteria – $LAB$, Escherichia coli – $Ec$, and coagulase-positive staphylococci – $Sa$ along the ripening. Cheese pH, acidity, and moisture, fat, and protein contents were quantified, as well as $LAB$, $Ec$, and $Sa$ concentrations. Richards and simplified Lotka-Volterra models were used to describe the microbial kinetic data. The fits were assessed by statistical indices, and the Monte-Carlo method was applied to identifiability analysis. Cheese moisture was reduced along the ripening, increasing protein concentration and acidity values. Cheese pH showed a reduction followed by an increase. $LAB$ concentration increased to the stationary phase after a few days; $Ec$ and $Sa$ concentrations increased and then decreased due to interactions with $LAB$ and low moisture content. Mathematical models successfully described the kinetics of $LAB$, $Ec$, and $Sa$ in cheese throughout ripening. Most parameters were not correlated to each other and were estimated with narrow confidence intervals.