Investigating the impact of a natural whey starter culture on the microbiological and physicochemical attributes of an artisanal cheese model.

Minas Gerais is known for producing raw milk artisanal cheeses, particularly Serra da Canastra. These cheeses are traditionally produced using a natural whey starter culture (NWS) known as pingo. The role of pingo in shaping cheese characteristics remains poorly understood. This research evaluated the microbiological and physicochemical effects of pingo on the artisanal cheese using a laboratory-scale model. Experimental cheeses were produced with pingo using two input frameworks: raw milk with high bacterial content and thermized milk with lower bacterial content. Control cheeses were made without pingo. Samples were analyzed during production and over 60 days of ripening for microbial counts (lactic acid bacteria (LAB), coliforms and Escherichia coli), pH, a, acidity and NaCl content. The microbial composition was determined by 16S rRNA sequencing. The logistic model was adjusted during 24 h of manufacture and the Weibull model was adjusted during ripening. Results indicated that during the production of the cheeses the maximum growth rate (μ) for E. coli was 25 % lower in cheeses produced with thermized milk and NWS compared to cheese without the addition of NWS. In raw milk cheeses, μ for E. coli was 2.3 to 3.0 times higher and no effect of NWS was observed, suggesting that NWS inhibits the growth of indicator microorganisms during cheese manufacturing only when the initial contaminant count is low. The time for the first decimal reduction (δ) of E. coli and coliforms during cheese ripening decreased by half with the addition of pingo, regardless of the type of milk used. The main genera identified in NWS was Streptococcus and a low relative abundance of Lactococcus. Cheeses produced with NWS presented a high prevalence of Streptococcus, followed by Lactococcus and Lactobacillus. In contrast, the cheese produced with raw milk and without NWS presented a high prevalence of Lactococcus. This study highlights the crucial role of pingo in reducing microbial loads and enhancing cheese safety, particularly when high- quality milk with low bacterial content is used, but its effectiveness is limited in poor-quality milk frameworks.