## 4 Discussion
equorum_ were frequently found to characterize Southern-European fermented meat products because they preferred relatively high pH and low fermentation temperatures [6; 10; 14; 54; 58; 59]. Spanish fermented meat products displayed a high relative abundance of _S. equorum_, but exhibited a greater CNS species diversity. The latter was largely due to the presence of _S. xylosus_, _S. saprophyticus_, _S. sciuri_, _S. gallinarum_, _S. carnosus_, and _S. vitulinus_, which have also previously been found in spontaneously fermented Southern-European fermented meat products [14; 60; 61; 62; 63]. When compared to French and Italian fermented meat products, the occurrence of less common genera and species and the overall lower bacterial loads in Spanish products suggest differences on the level of starter culture application, either because the process is based on spontaneous fermentation or because of poor adaptation of the starter culture bacteria involved to the processing conditions [6, 16, 64]. In contrast, the relatively high abundance of _S. carnosus_ in Belgian and German fermented meat products does indicate starter culture use, as this species is not common in the natural microbiota of spontaneously fermented meat products but routinely used as a starter culture in Northern Europe [8, 54, 65, 66]. Noteworthy in that respect was the case of the Belgian product BE3, which was characterized by a somewhat atypical higher pH of 5.7 for its region of production. Although _S. carnosus_ was still found, the relative abundance of _S. xylosus_ increased and _S. saprophyticus_ and _S. vitulinus_ also emerged, all of which have been encountered in previous studies in spontaneously fermented meat products of similar acidity [14, 67, 68]. As fermented meat products, BE1 and BE3 were manufactured by the same producer, it is likely that the same starter culture was used but that different communities were obtained, due to differences in the processing conditions, although details about the latter are not known. This pronounced difference in the composition of the CNS communities underlines the influence of the pH as a major processing factor, as well as the influence of the processing conditions on the structure of the CNS communities in meat fermentation, whether or not starter cultures are used [7, 15, 64]. Compared to the culture-dependent methodology applied previously on the same commercial fermented meat products [6], amplicon-based HTS allowed for the charting of the CNS communities with far greater resolution (Table 3). Whereas the dominant CNS species were comparable, amplicon-based HTS allowed for the uncovering of several subdominant CNS species. Failure of detection of the latter by culture-dependent methods was due to limitations imposed by the cultivation step and the subsequent work needed to obtain a sufficient number of isolates, fingerprints, and sequencing data. This showcases the capability of amplicon-based HTS methods to rapidly unravel complex microbial communities in fermented foods in a satisfactory degree of detail [25]. Several VOCs were detected in the fermented meat products examined, which could either be related to microbial metabolism (e.g., acetoin, acetic acid, and 3-methylbutanal), the addition of certain spices and herbs (e.g., terpenes and sulfur compounds), or the processing applied (e.g., the presence of phenolic compounds due to smoking) [41, 69, 70, 71, 72, 73]. However, no clear trends relating VOC compositions to the presence of certain microbial groups or unique processing practices could be distinguished. For this purpose, a more quantitative approach targeting specific VOCs may be needed.