Selective enrichment of the raw milk microbiota in cheese production: Concept of a natural adjunct milk culture

Abstract

In cheese production, microorganisms are usually added at the beginning of the process as primary starters to drive curd acidification, while secondary microorganisms, with other pro-technological features important for cheese ripening, are added as selected cultures. This research aimed to investigate the possibilities of influencing and selecting the raw milk microbiota using artisanal traditional methods, providing a simple method to produce a natural supplementary culture. We investigated the production of an enriched raw milk whey culture (eRWC), a natural adjunct microbial culture produced from mixing an enriched raw milk (eRM) with a natural whey culture (NWC). The raw milk was enriched by spontaneous fermentation for 21 d at 10°C. Three milk enrichment protocols were tested: heat treatment before incubation, heat treatment plus salt addition, and no treatment. The eRMs were then co-fermented with NWC (ratio of 1:10) at 38°C for 6 h (young eRWC) and 22 h (old eRWC). Microbial diversity during cultures’ preparation was evaluated through the determination of colony forming units on selective growth media, and next-generation sequencing (16S rRNA gene amplicon sequencing). The enrichment step increased the streptococci and lactobacilli but reduced microbial richness and diversity of the eRMs. Although the lactic acid bacteria viable count was not significantly different between the eRWCs, they harbored higher microbial richness and diversity than NWC. Natural adjunct cultures were then tested in cheese making trials, following the microbial development, and assessing the chemical quality of the 120 d ripened cheeses. The use of eRWCs slowed the curd acidification in the first hours of cheese making but the pH 24 h after production settled to equal values for all the cheeses. Although the use of diverse eRWCs contributed to having a richer and more diverse microbiota in the early stages of cheese making, their effect decreased over time during ripening, showing an inferior effect to the raw milk microbiota. Even if more research is needed, the optimization of such a tool could be an alternative to the practice of isolating, geno-pheno-typing, and formulating mixed-defined-strain adjunct cultures that require knowledge and facilities not always available for artisanal cheese makers.

Proteomics Parameters for Assessing Authenticity of Grated Grana Padano PDO Cheese: Results from a Three-Year Survey

“…This situation suggests that this grated cheese is not authentic GP. It was previously demonstrated that deviations from the traditional manufacturing process of GP, such as the pasteurization or centrifugation of milk, the usage of selected starters or adjunct cultures, and mechanized curd processing, all have an impact on the final release of FAAs [15,32,33]. Indeed, the discriminating power considering the whole FAA profile is that each cheese is evaluated on the basis of 21 variables at the same time.…”

Evaluation Dangke Cheese Processing by Edible Film Coating Made from Whey Combined with Konjac Flour

“…Several factors influence the type and variety of cheese, the degree of milk acidity in the curd formation process, the type of microorganism used for fermentation [34], and the nutritional composition of milk in cheese making, including fat content, also including incubation temperature, humidity, production process, and ripening time in processing cheese [35,36].…”

Microbial Evolution in Artisanal Pecorino-like Cheeses Produced from Two Farms Managing Two Different Breeds of Sheep (Comisana and Lacaune)

“…Thus, monitoring microbiota composition and its evolution during fermentation and ripening is crucial for obtaining products with optimal sensory properties and safety characteristics [ 19 ]. Much effort has been put into investigating raw milk microbial communities to improve cheese production and safety due to their importance to the world’s population [ 20 , 21 ].…”