Microbial characterization of an artisanal production of Robiola di Roccaverano cheese

Abstract

Robiola di Roccaverano is a PDO (Protected Designation of Origin) soft cheese made with raw goat's milk, from the Piedmont region of Italy. The peculiarity of this cheese is that during the manufacturing process, a Natural Starter Culture (NSC) is added to raw milk. In this study, the viable microorganisms of technological interest, including Lactic Acid Bacteria (LAB) and fungal populations were examined in samples of raw milk, NSC, fresh and ripened cheese collected from one dairy by means of culture-dependent techniques. Firstly, the isolated colonies were analyzed by means of Random Amplify Polymorphic DNA-PCR (RAPD-PCR) and strains with similar fingerprint were clustered together. Further, representative isolates of each group were subjected to 16S rDNA or 26S rDNA sequencing. Finally, species-specific PCR was conducted to distinguish the Lactococcus lactis subspecies lactis and cremoris. Among the studied LAB, 13 RAPD-profiles were Page 2 of 32 ScholarOne support: (434) 964 4100 Journal of Dairy Science 3 obtained, corresponding to different bacterial species or subspecies. Concerning mould and yeast isolates, 5 species were found which coincided with RAPD-type. Observing the strains isolated in the study, Lactococcus lactis was the most prevalent species in raw milk and NSC samples. Instead, Leuconostoc mesenteroides was the predominant species identified in 5-and 15-days cheese isolates. Furthermore, while only these two species were detected in NSC, in raw milk and cheese Enterococcus and Lactobacillus genera were respectively found. Concerning the mould and yeast isolates, in NSC Kluyveromices spp. was mainly found, instead, in cheese samples representative species were Geotrichum candidum and Yarrowia lipolytica. Finally, the raw milk and cheese safety were evaluated and the samples complied with the standard required by the European Commission Regulation 2073/2005.

Short communication: High-throughput sequencing approach to investigate Italian artisanal cheese production

“…On the other hand, Leuconostoc, found in low proportion in NMS, has a poor starter function but is involved in cheese maturation through the production of aromatic compounds such as acethaldeydes, dyacetl, and acetoin (McSweeney and Sousa, 2000). Microbial characterization of Robiola di Roccaverano production has been performed in previous studies through culture-dependent analysis investigating LAB populations (Biolcati et al, 2019(Biolcati et al, , 2020. These studies highlighted the elevated number of LAB in NMS and cheese, in which Lc.…”

Mycobiota Composition of Robiola di Roccaverano Cheese along the Production Chain

“…HTS and the combination of several methodologies to study food-associated microbiota and mycobiota may allow to obtain more detailed information on the typical microflora of artisanal dairy products. The samples analyzed in this study were also matters of a past work already published aimed to characterize the bacterial and fungal diversity of a Robiola di Roccaverano production with culture-dependent techniques [13]. The genera highly detected in the present study, such as G. candidum, Y. lipolytica, and K. marxianus were also among the most abundant strains isolated and identified by RAPD-PCR [13].…”

“…The samples analyzed in this study were also matters of a past work already published aimed to characterize the bacterial and fungal diversity of a Robiola di Roccaverano production with culture-dependent techniques [13]. The genera highly detected in the present study, such as G. candidum, Y. lipolytica, and K. marxianus were also among the most abundant strains isolated and identified by RAPD-PCR [13]. Furthermore, few colonies belonging to the species T. coremiiforme and S. silvae isolated in the past study were detected by HTS.…”

“…Several works have been performed for the characterization of the microbiota of Robiola di Roccaverano cheese, however the fungal community involved in this cheese production remains less explored [13,16]. Thus, the present study aimed to understand the variation of the fungal community in the different steps of production of the cheese-making process of Robiola di Roccaverano cheese.…”

“…However, at least 50% of the milk used for the production must be goat's milk. During manufacturing process, thermization process are not allowed and natural milk cultures (NMC) containing mainly Lactococcus lactis are inoculated together with animal rennet for curd formation [12][13][14]. NMC is obtained by back-slopping process where a small amount of the previous days fermented milk is inoculated into fresh milk to start the fermentation process.…”