Dynamics of Whole and Lysed Bacterial Cells during Parmigiano-Reggiano Cheese Production and Ripening

Abstract

Microbial succession during Parmigiano-Reggiano cheesemaking was monitored by length heterogeneity PCR (LH-PCR), considering the intact and lysed cells at different stages of cheese production and ripening. When starter species underwent autolysis, species coming from milk were able to grow. For the first time, the LH-PCR technique was applied to study a fermented food.Parmigiano-Reggiano (PR) is a protected-designation-of-origin cheese, produced in specific areas of Northern Italy. It is a hard-textured, cooked, and long-ripened cheese made from raw cow's milk supplemented with natural whey starter rich in thermophilic lactic acid bacteria (LAB). Microbiological features of PR have been studied, isolating on traditional growth media a large number of strains from a large amount of samples representative of production and of the earlier and advanced stages of ripening (2, 3). Other studies have focused on the biodiversity of different strains of Lactobacillus helveticus isolated from natural whey cultures (6, 7). These previous studies showed the microbial biodiversity of PR but not its real microbial succession during production and ripening, and the use of culture-dependent methods could have underestimated the less-abundant components of microflora, which are equally important for cheese ripening and flavor development (15). Thus, the microbial ecology of PR still appears not to be completely understood. From this perspective, a detailed knowledge of LAB dynamics during the manufacturing and ripening stages is necessary for a deeper insight into the complex processes which contribute to the development of this appreciated cheese.In the present study, length heterogeneity PCR (LH-PCR) was used to monitor the microbial dynamics during 24 months of PR ripening for both the whole and lysed cells. The availability of PR twin wheels allowed us to have samples representative of the subsequent stages of the same cheesemaking process.In our opinion, the new findings in this article contribute to a better understanding of microbial dynamics in a complex fermented ecosystem.Cheesemaking. A unique cheese factory was selected for its equipment and technological conditions in order to obtain a suitable number of PR twin wheels. The same milk was distributed in equal volumes in eight vats and was worked according to PR production standards.Thirty-four liters of natural whey starter was added in each vat, containing 1,070 liters of milk (525 liters of partially skimmed evening milk and 545 liters of whole morning milk), bringing the pH of the mixture to 6.20. After cheesemaking and molding, the wheels, two from each vat, were held for 3 days and frequently turned to enable complete whey drainage. They were then salted by immersion in brine at 300 g NaCl ⅐ liter Ϫ1 for 23 days. Ripening was carried out in aging rooms with 85% relative humidity and a temperature of about 18°C for 24 months.Cheese sampling and bacterial recovery. Samples were collected from milk to cheese ripened for 24 months. Aliquots of the total mass of raw...

Whey starter addition during maturation of evening milk: effects on some characteristics of cheese milk and Parmigiano–Reggiano cheese

“…Mesophilic LAB reached their maximum growth in the seventh month of ripening for all the theses, while the thermophilic LAB showed the highest levels at the beginning and then gradually decreased. These results are in agreement with the observation reported in other studies (Coppola et al 1997;Gatti et al 2008). The results of the present study show that the addition of LAB during natural creaming of milk using young whey starter does not affect the normal succession of thermophilic and mesophilic LAB in the cheese, and their counts in different stages of ripening is typical for Parmigiano-Reggiano cheese (Coppola et al 1997 and2000;Gatti et al 2008;Neviani et al 2009).…”

“…Then, the consumption of lactose and the decrease of ripening temperature limit their growth, favouring cells autolysis. Enzymes released by SLAB induce the production of compounds essential for NSLAB metabolism (Gatti et al 2008).…”

Identification and characterization of wild lactobacilli and pediococci from spontaneously fermented Mountain Cheese

“…Calculation of similarity of the PCR fingerprinting profiles was based on the Pearson productemoment correlation coefficient. Isolates with a similarity coefficient higher than 85% were considered belonging to the same biotype, as described by Gatti et al (2008).…”

Characterization by length heterogeneity (LH)-PCR of a hydrogen-producing community obtained in dark fermentation using coastal lake sediment as an inoculum

“…In this study, the ABI collection software allowed the distinction of amplicons differing in size of only a few base pairs and the accurate detection of the relative ratio for each of them, including the less abundant amplicons. The LH-PCR profiling is reported as a fast, reliable, and sensitive method for community studies in environmental samples, biological processes, and bioreactors, where diversity is present on the class/phylum level [16,[20][21][22]. In this study, the taxonomic identification of community members as species of Clostridium is based on a limited number of clones that may not represent the whole community.…”