## 3 Results and Discussion
### Biopreservation of Chocolate Mousse  
Biopreservation is a method for preserving food quality and prolonging food shelf life via the introduction of substances of plant origin, animal origin, or microbial origin (metabolic substances with antimicrobial activity or living microorganisms (most commonly lactobacilli and bifidobacteria) that produce metabolites with high antimicrobial activity). CM variants with free or encapsulated _Lactobacillus helveticus_ 2/20 cells and peppermit EO were prepared. According to Bulgarian State Standards, the resulting CM variants should have a shelf life of 6 months in the frozen state and 3 weeks under refrigerated conditions (Figure 8a-f). Figure 8: Biopreservation of CM. (**a**) control sample–pH. (**b**) biopsyerved sample with peppermit EO–pH. (**c**) biopsyerved with encapsulated lactobacilli cells sample–pH and viable cells. (**d**) biopsyerved with free lactobacilli cells sample–pH and viable cells. (**e**) biopsyerved with free lactobacilli cells and peppermit EO sample–pH and viable cells. (**f**) biopsyerved with encapsulated lactobacilli cells and peppermit EO sample–pH and viable cells. The changes in the pH and the microflora of the CM variants were monitored during the storage period of up to 20 days. The changes in the pH values during the storage process of the CM were slight (Figure 8a-f). The pH was maintained almost constant in the CM variants biopreserved with EOs, and the pH slightly decreased in the CM biopreserved with _Lactobacillus heleticus_ 2/20 cells and EOs. Throughout the storage period, the probiotic strain retained a high concentration of viable cells (10\({}^{5}\) cfu/g) (Figure 8a-f). With regard to pathogenic microorganisms, the CM variants met the standard requirements, and the number of active cells of mesophilic aerobic and facultatively anaerobic microorganisms, fungi, and yeasts was up to 10\({}^{2}\) cfu/g (Table 7). The number of viable _E. coli_ cells in all CM variants from the 1 st to the 20 th day of storage was below 10 cfu/g. The number of viable _S. aureus_ cells in all CM variants from the 1 st to the 20 th day of storage was below 100 cfu/g. No _Salmonella_ sp. cells were found in any of the CM variants from the 1 st to the 20 th day of storage. The unwanted microflora in the CM variants biopreserved with lactobacilli and EO gradually decreased during the storage period, and no viable cells of pathogenic or saprophytic microorganisms after the 20 th day were determined (Table 7). This could be explained by the demonstrated antimicrobial activity of the probiotic strain _Lactobacillus heleticus_ 2/20 against mesophilic aerobic and facultatively anaerobic microorganisms, fungi, and yeasts, as well as the beneficial effect of peppermint, E.O. The CM variants were evaluated according to six criteria: appearance, characteristic smell, sweetness, taste, aftertaste, and texture, with each criterion ranging from 0 (worst evaluation) to 9 (best evaluation) (Figure 9a-e). It has been established that the different CM variants have good organoleptic indicators. The CM variants preserved with free or encapsulated _Lactobacillus heleticus_ 2/20 cells and their combination with peppermint essential oil received the highest marks (Figure 9a-e). The results obtained are consistent with those of [PERSON] et al. (2020) [62] and are of great importance for food emulsion production, since the introduction of EOs and probiotic bacteria would avoid additional contamination with pathogens and saprophytes [63]. Moreover, in addition to biopreservation, the intake of food enriched with probiotic bacteria ensures the entrance of a significant number of viable cells of probiotic microorganisms into the gastrointestinal tract. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**1 st Day**} & \multicolumn{2}{c}{**5 th Day**} & \multicolumn{2}{c}{**10 th Day**} & \multicolumn{2}{c}{**15 th Day**} & \multicolumn{2}{c}{**20 th Day**} \\ \hline
**CM Variant** & \begin{tabular}{c} **TBA,** \\ **cfu/g** \\ \end{tabular}  &