The Natural Whey Starter Used in the Production of Grana Padano and Parmigiano Reggiano PDO Cheeses: A Complex Microbial Community.

Natural whey starter (NWS) is an undefined complex culture used in the production of Grana Padano and Parmigiano Reggiano PDO cheeses. The aim of this review is to discuss, in light of the latest research results, the role of NWS as a primary player in the cheese-making process, considering the microbial community scenario. NWS is traditionally produced by fermenting part of the whey collected at the end of a previous cheese-making process. The method used to produce NWS, based on the back-slopping principle, favors the selection of a microbiota composed mainly of thermophilic lactic acid bacteria. This method of preparation induces the survival of several different species and biotypes. The presence of such a mixture of strains facilitates the development of a natural starter characterized by a remarkable ability to adapt to non-standardized cheese-making parameters. NWS is a microbial community whose activity is not simply the result of the sum of the activities of individual microorganisms, but rather the activity of the community as a whole, in which each individual bacterial cell responds to the presence of the others. According to this traditional protocol, the NWS becomes the 'microbiological bond' between cheeses over time.