From Raw Milk Microbiome to Cheese: The Challenge of Indigenous Natural Starter Culture Exploitation

A freeze-dried natural starter culture (NSC) was developed and assessed for its suitability in producing a semi-cooked, 60-day-ripened cheese resembling the protected designation of origin (PDO) Pecorino Sardo. The culture, derived from raw ewe’s milk from a dairy farm involved in the study, without thermal decontamination to preserve indigenous microbiota, was enriched with two strain-level-characterised, biodiverse mixtures of Streptococcus thermophilus (Str-mix) and Lactobacillus delbrueckii (Lb-mix). This study evaluated the technological robustness and adaptability of NSC enriched with biodiverse Str-mix and Lb-mix across three different artisanal dairy-processing environments with varying milk compositions and equipment levels at plants located in different geographic areas. During cheesemaking, technological, physico-chemical, and compositional parameters were monitored, along with microbial characterisation of milks and 1-day cheeses. After 60 days of ripening, cheeses were characterised from the microbiological, physico-chemical, and compositional perspectives. Furthermore, nutritional labelling was established, and consumer acceptance was determined. Results showed that the starter (NSC + Str-mix + Lb-mix) demonstrated strong and reproducible technological performance in all dairies, regardless of the milk’s chemical and microbial composition variability. Sensory quality was preserved in cheeses ripened for up to 180 days. These preliminary findings seem to support the use of freeze-dried, raw-milk-derived natural cultures in artisanal cheesemaking as a way to preserve microbial diversity and to reconnect with traditional practices that enhance both the tangible and intangible assets of modern society.