Invited review: Microbial evolution in raw-milk, long-ripened cheeses produced using undefined natural whey starters

Abstract

The robustness of the starter culture during cheese fermentation is enhanced by the presence of a rich consortium of microbes. Natural starters are consortia of microbes undoubtedly richer than selected starters. Among natural starters, natural whey starters (NWS) are the most common cultures currently used to produce different varieties of cheeses. Undefined NWS are typically used for Italian cooked, long-ripened, extra-hard, raw milk cheeses, such as Parmigiano Reggiano and Grana Padano. Together with raw milk microbiota, NWS are responsible for most cheese characteristics. The microbial ecology of these 2 cheese varieties is based on a complex interaction among starter lactic acid bacteria (SLAB) and nonstarter lactic acid bacteria (NSLAB), which are characterized by their different abilities to grow in a changing substrate. This review aims to summarize the latest findings on Parmigiano Reggiano and Grana Padano to better understand the dynamics of SLAB, which mainly arise from NWS, and NSLAB, which mainly arise from raw milk, and their possible role in determining the characteristics of these cheeses. The review is presented in 4 main sections. The first summarizes the main microbiological and chemical properties of the ripened cheese as determined by cheese-making process variables, as these variables may affect microbial growth. The second describes the microbiota of raw milk as affected by specific milk treatments, from milking to the filling of the cheese milk vat. The third describes the microbiota of NWS, and the fourth reviews the knowledge available on microbial dynamics from curd to ripened cheese. As the dynamics and functionality of complex undefined NWS is one of the most important areas of focus in current food microbiology research, this review may serve as a good starting point for implementing future studies on microbial diversity and functionality of undefined cheese starter cultures.

Ion-Exchange Chromatographic Method for the Determination of the Free Amino Acid Composition of Cheese and Other Dairy Products: an Inter-Laboratory Validation Study

“…The common rationale behind this fact is that all these cheeses (1) are made from raw milk produced in a restricted geographical area, (2) following a well-defined traditional manufacturing process, and (3) using a natural whey culture daily prepared from the previous cheesemaking. These provisions are detailed in the product specification for PDO protection (European Council 2012) and guarantee that the same relevant microbial species (LAB and NSLAB) are constantly transferred from milk into the cheese (Gatti et al 2014). As a result, for each cheese type, the proteolytic pathways occurring during ripening are repeatable and hence the resulting FAA pattern as well is repeatable and characteristic.…”

“…During cheese ripening, protein is progressively degraded by a number of proteolytic enzymes including (1) chymosin, (2) indigenous milk proteases, and (3) proteases and peptidases from both starter (LAB) and non-starter lactic acid bacteria (NSLAB), mainly released after cell lysis (Borsting et al 2012;Gatti et al 2014). According to the manufacturing process and ripening period, up to 20-25% of the cheese protein may be split into FAAs, which can represent over 50% of the soluble N fraction (Sousa et al 2001;Pellegrino et al 2013).…”

Prevalence and Antimicrobial Resistance Assessment of Subclinical Mastitis in Milk Samples From Selected Dairy Farms

“…Milk also serves as an optimum medium for the propagation of various pathogenic and spoilage microorganisms (Minst et al, 2012;Gatti et al, 2013). These pathogens invade the mammary glands, develop and multiply, producing some toxic substances that results in inflammation, reduced milk production and altered milk quality, leading to a clinical condition known as mastitis (Oliver and Muranda, 2012;Rall et al, 2013).…”

Microbiota of an Italian Grana-Like Cheese during Manufacture and Ripening, Unraveled by 16S rRNA-Based Approaches

“…Different microbial populations coexist and interact, contributing through their metabolism to the development of taste, aroma, texture, shelf-life, and safety (6). In particular, the microbial ecology of long-ripened cheeses, produced from raw milk and using whey starters, is based on the complex interaction among starter lactic acid bacteria (SLAB) and nonstarter lactic acid bacteria (NSLAB) (7). SLAB give their contributions in the early stages of the cheese making, while NSLAB, which are able to use other carbon sources apart from lactose, become the dominant microbiota of the ripened cheeses (8) and are responsible for the flavor and texture of the cheeses due to their proteolytic and lipolytic activities (7).…”