## 2 Results and Discussion
### The Composition of Volatile Compounds
The presence of LAB enzymes leads to the hydrolysis of proteins, polypeptides, and free amino acids, which are aromatic compounds or their precursors [4]. The metabolic reactions in dry fermented meat and flavour additives, such as pepper, garlic, and other spices, are critical to the typical sensory characteristics of both odour and flavour [21; 22]. In our study, the probiotic sausages showed a significantly higher level of acidic volatile compounds, mainly acetic acid, compared with that in the control samples both after fermentation and during storage, which, in the sensory assessment, contributed to a more intense sour flavour. The fermentation processes of carbohydrates taking place in meat products due to the presence of LAB increase the content of lactic and acetic acids, causing a decrease in the pH [22]. The increase in the acidity of the product may be positively perceived by consumers as an expression of traditional food production processes; this has been confirmed using the high overall quality scores obtained for probiotic sausages. The decrease in the pH inhibits the growth and multiplication of undesirable microorganisms, including putrefractive bacteria, thus extending the shelf life [4]. Some studies have found 26 terpene compounds in dry fermented sausages, mainly due to the addition of spices [19; 21]. The metabolism of microorganisms, including moulds and yeast, in the production of terpenes should be considered [23]. The total content of terpenes increased during storage in all the sausage samples studied. [PERSON] et al. [24] also observed an increase in terpene contents during the fermentation of Pitina sausages. According to the authors, the reason for this was the loss of water during the fermentation process, which increased the proportion of fat, in which terpenes are easily soluble. In the case of the control sausages after fermentation and after 12 weeks of storage, the level of terpenes, especially those of 3-carene and alpha-limonene, was higher than that in the sausages with probiotics. Different terpene concentrations, especially in sample groups P0 and K12 (Table 3), could be attributed at least partially to the sausage matrix effect. Thus, the terpenes were differentially released into the headspace \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **Compound Name** & **K0** & **K6** & **K12** & **P0** & **P6** & **P12** \\ \hline Alpha-Terpinolen & 1.77 c & 1.91 cd & 1.94 d & 1.33 a & 1.49 ab & 1.59 b \\ \hline Linalol & 0.83 a & 0.82 a & 0.74 a & 0.46 c & 0.57 b & 0.60 b \\ \hline Terpinen-4-ol & 1.22 a & 1.20 a & 1.21 a & 0.93 b & 1.26 a & 1.13 ab \\ \hline Alpha-Terpineol & 0.29 d & 0.27 c & 0.23 bc & 0.17 a & 0.20 ab & 0.22 abc \\ \hline Alpha-Copaene & 0.16 ab & 0.14 a & 0.17 ab & 0.16 ab & 0.19 bc & 0.21 c \\ \hline Beta-Elemene & 0.12 a & 0.10 a & 0.11 a & 0.07 b & 0.10 a & 0.11 a \\ \hline Beta-Caryophyllene & 5.38 a & 4.66 a & 5.24 a & 3.42 b & 4.95 a & 4.93 a \\ \hline Alpha-Caryophyllene & 0.24 a & 0.19 ab & 0.22 a & 0.15 b & 0.21 a & 0.22 a \\ \hline Beta-Selinene & 0.12 a & 0.11 ab & 0.11 ab & 0.09 b & 0.11 ab & 0.13 a \\ \hline Alpha-Selinene & 0.09 a & 0.08 a & 0.09 a & 0.06 b & 0.08 a & 0.09 a \\ \hline Total terpenes & 71.64 a & 72.12 a & 76.83 c & 66.12 b & 71.33 a & 71.27 a \\ \hline \hline Explanatory notes: Control sausages without \(L\). _rhammosus_ LOCK900 addition: K0-after ripening process, K6-after 6 weeks of storage, K12-after 12 weeks of storage. Probiotic sausages with \(L\). _rhammosus_ LOCK900 addition: P0-after ripening process, P6-after 6 weeks of storage, P12-after 12 weeks of storage. Means in the same row followed by different letters represent significant differences (\(\alpha\leq 0.05\)). & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._at the end of storage and specifically in the control samples; this could be attributed to the different pH values (among other things). A partially similar effect was observed in the study by [PERSON] et al. (2020).