## 4 Discussion
Nevertheless, cheese flavor is rather a result of a balance between the concentrations of volatile compounds detected in cheese than a contribution of particular components [20]. For the HS-SPME GC/MS analysis, samples at the beginning and after 3 days of storage were tested. The incorporation of free or immobilized cells affected the aroma profile of cheese, in accordance with previous studies on dairy products fortified with lactic acid bacteria [32,33]. Indeed, regarding esters, [PERSON] et al. [20] noted that cheese samples fortified with free _L. casei_ cells exhibited higher amounts of ethyl lexanoate and ethyl decanoate compared to control cheese, as well as to cheese samples with immobilized cells on whey protein. Similarly, [PERSON] et al. [33] reported the detection of ethyl decanoate in soft whey cheese with free and immobilized _L. paracaei_ cells; however, it was undetectable in the control cheese. In total, the esters identified in cheese samples are known to produce a fruity aroma in foods [34,44]. The acids found at increased concentrations in the KFP and KIP samples were sorbic, octanoic and decanoic acid, which were at higher amounts in the KFP samples--results that are in accordance with previous studies in dairy products fortified with probiotics [33,34]. Among alcohols, the most abundant were 3-methyl-1-butanol and 2-phenylethanol in all samples and are described as exerting malt notes and burnt aroma [4]. Carbonyl compounds detected in cheese samples belong to aldehydes and ketones, but aldehydes were in low concentrations due to their reduction to alcohols [35]. 3-methyl-butanal and hexanal detected only in the KFP and KIP samples were similarly identified in cheese samples fortified with free or immobilized lactic acid bacteria, in accordance with previous studies [20]. Of note, 3-methyl-butanal is also present in other cheeses like Camembert and aged Cheddar, adding a fruity aroma [45]. Furthermore, hydrocarbons were also present in cheese, mainly in the KFP and KIP samples. In general, hydrocarbons do not directly affect the aroma profile of cheese. However, they act as precursors to other volatile compounds [46]. Notably, PCA, which was carried out in order to evaluate the effect of _P. acidilactici_ ORE5 on the volatile profile of Katiki Domokou cheese, revealed that the incorporation of free and immobilized cells affected the concentrations of volatile compounds, which can be attributed to their fermentation activity, while similar results have been reported in previous studies [20,46]. Dairy products, specifically cheeses, are characterized by a certain microbiome, which differs between different types of cheese, depending on a variety of factors, such as milk source, the starter and adjunct cultures, the cheese-making process, the geographical region and the terroric [36]. Although the plate count method provides a quantitative assessment of the microbial composition of the product, it has some limitations due to its sensitivity, as well as its inability sometimes to distinguish between colonies. Hence, it is often recommended to combine the plate count method with other techniques, such as molecular methods (e.g., DNA-based techniques), to obtain a more comprehensive understanding of the microbial community [47]. In this study, the effect of _P. acidilactici_ ORE5 cells incorporated into Katiki Domokou cheese on the cheese microbiome was investigated after 16S rRNA sequencing. The Shannon index, which measures the diversity of species present in a sample, as well as the Simpson index, which assesses the dominance of species within the sample, were also calculated. Concerning the results, a greater bacterial diversity was observed as a result of the incorporation of immobilized cells in the cheese sample, which has also been noted by [PERSON] et al. [48].