# Microbiota \"Fingerprint\" of Greek Feta Cheese through Ripening
## 4 Discussion  
The aim of the study was to characterize the microbiota 'fingerprint' of Feta cheese using culture-dependent methods such as MALDI-TOF MS during the ripening process. In Greece, one of the most embematic cheese is Feta cheese as it is a highly consumed PDO product, by far the most popular and therefore it is crucial to understand and reveal the whole microbiota present in the cheese. There is a growing interest in the identification of microbiota, present in the Feta cheese core, as this part of bacterial communities can enhance the shelf-life of the cheese, determine its safety, its functionality and quality, as well as its nutritional properties. The number of live microorganisms in cheees can vary significantly, depending on product manufacturing process, conditions of storage, and ripening time. According to the CODEX standards for fermented milk products, the minimum number of starter culture bacteria in yogurt is 7.0 log cfu/g [26]. In our results, the total viable microorganisms ranged from 7.79 log cfu/g (for three months ripening) to 7.80 log cfu/g (for six months ripening). Various bacterial communities participating in the microbiota of Feta cheese have been studied by researchers in the past [6; 8; 12; 27], yet only one study, as it is mentioned before, provided some data regarding the dominant lactic acid bacteria of traditional Feta cheese. Cheese is a living ecosystem whose bacterial elements originate from the milk and the dairy establishment (equipment, procedures, facilities, etc.) [28; 29]. These microorganisms are responsible for the course of the fermentations and it is their mutual interaction resulting to the sensorial characteristics of the cheese. Besides their technological properties mainly important to the industry, most of these bacteria have beneficial impact to human health, also known as probiotics. Hence, there are often a lot of reasons based on quality and health aspects that dairy microorganisms, and particularly the ones from the most popular products, should be identified and thoroughly studied. MALDI-TOF MS is considered as a method of choice for analysis of complex mixtures of bacterial proteins and represents a simple, reliable, and cost-saving tool for the rapid taxonomic characterization of microflora in dairy products not only at the genus level, but also at the level of species and subspecies [30; 31; 32]. The enrichment of the available data bases with reference material could be the key point to increase the discriminatory ability of the method, in cases where there is the need to distinguish close-related phylogenetic strains. The technique of MALDI-TOF MS has been applied to identify lactic acid bacteria from French Maroilles cheese and achieved the identification of LAB strains from Maroilles cheese, made from raw and pasteurized milk. In another study, were analyzed the derivatives from fruits with a genotyping method such as 16S rRNA gene sequencing and the culture dependent method such as MALDI-TOF MS to identify LAB species. The identification match for both techniques was 86% [33; 34]. Feta cheese, according to its standards, must ripen for at least two months before consumption. However, Feta cheese continues to ripen after that period. Accordingly, the present research studied and verified the microbiota of the cheese and their alterations during a prolonged ripening time, ranging from the three to six months. The Lactobacillus genus being the most abundant of LABs, plays a crucial role during fermentations due to their diverse fermentative properties (heterofermentative, facultative heterofermentative) as well as their lipolytic and proteolytic activity. Our results were in accordance with the study in French Maroilles cheese in which, among the three identified genera, namely Lactobacillus, Leuconstoc, and Enterococcus, Lactobacillus was the most prominent genus with the _Lb. brevis, Lib. plantarum, Lib. curvatus, Lib. paracasei, Lib. rhamnosus, Lib. parabuchneri, and Lib. fructivorans_ species to be dominant in the Feta cheese microbiota [35].