Characterisation of the microflora contaminating the wooden vats used for traditional Sicilian cheese production

Abstract

Traditional Sicilian cheese productions are carried out employing traditional wooden vats, called tina. Many studies have highlighted the beneficial role of wooden dairy equipment by contributing to enriching the milk microflora and improving the acidification processes. The present work was undertaken to evaluate the safety of the wooden vats used to coagulate milk. To this purpose, the different microbial populations hosted onto the internal surfaces of the vats used to produce two different stretched cheeses, namely Caciocavallo Palermitano and Vastedda della valle del Belìce DOP, were investigated for the presence of spoilage and pathogenic microorganisms as well as for bacteria with inhibitory effect in vitro against pathogenic microorganisms. A wide biodiversity of protechnological lactic acid bacteria (LAB), in terms of species, was revealed. Several LAB inhibited the growth of Listeria monocytogenes ATCC 7644. The wooden vats analysed resulted safe for three main findings: absence of the main pathogenic species, presence of high levels of LAB, anti-Listeria activity of many LAB.

Microbial Activation of Wooden Vats Used for Traditional Cheese Production and Evolution of Neoformed Biofilms

“…in the biofilms analyzed was probably due to the acidic conditions generated by the development of LAB in whey, which inhibit the adhesion and survival of several microorganisms (4, 7). The estimated levels of LAB in the neoformed biofilms were comparable to those reported for the wooden vats used for years to produce traditional cheeses (4)(5)(6)(7)(8)19). Except for the vats activated with the NWSC, for which the dominance of LAB cocci was undoubtedly due to the added lactococci, a consistent dominance of LAB cocci over rods was also observed for the vats activated with the whey acidified spontaneously.…”

“…Except for the vats activated with the NWSC, for which the dominance of LAB cocci was undoubtedly due to the added lactococci, a consistent dominance of LAB cocci over rods was also observed for the vats activated with the whey acidified spontaneously. Thus, it is possible to state that the common observation of a dominance of LAB cocci in the wooden vat biofilms used to produce several cheeses in different countries (6,8,19) starts during the first steps of their activation with whey. Furthermore, it is worth noting that the mixed Lc.…”

“…Animal rennet pastes are coagulant agents that were recently demonstrated to contribute to LAB biodiversity (2); however, they cannot guarantee a constant supply of dairy LAB. In contrast, investigations carried out in Sicily showed that wooden vat surfaces provide all the dairy LAB species required for cheese production, both for fermentation (4,5,7,8) and during ripening (14).…”

“…Under these conditions, the desirable lactic acid bacteria (LAB) that transform curd into cheese (3) are provided only by the raw materials and/or the vat surfaces (4). The wooden vat surfaces host microbial biofilms that include dairy LAB (4)(5)(6)(7)(8).…”

Transfer, composition and technological characterization of the lactic acid bacterial populations of the wooden vats used to produce traditional stretched cheeses

“…Furthermore, it has been demonstrated that the aging on wooden planks reduces the presence of bacteria dangerous for humans, such as Listeria monocytogenes, showing instead a potential of wood for bioprotection against food pathogens (Mariani et al, 2011). Since several traditional cheeses are made in wooden vats, the microbial characterization of these recipients has been the object of different research groups, mainly Italian and French, in the last few years (Licitra et al, 2007;Lortal et al, 2009;Didienne et al, 2012;Settanni et al, 2012;Scatassa et al, 2015). They found LAB at dominant levels, while the undesired microorganisms, including coliforms and coagulase-positive staphylococci (CPS), were at very low densities and, overall, the presence of the pathogenic bacteria L. monocytogenes and Salmonella spp.…”