Fermented drinks are highly valued for their organoleptic and health-promoting properties. The most popular and appreciated are those based on milk in the form of fermented milks, but in recent years drinks based on plant matrices have been also gaining popularity. The most popular microorganisms used in such production are lactic acid bacteria (LAB) and Bifidobacterium bacteria. There are more and more suggestions indicating the potential of propionic acid fermentation bacteria in this application.

The aim of this study was to obtain fermented drinks based on a milk and plant matrix using mesophilic lactic acid bacteria (Lactococcus lactis ATCC 11454), propionic acid bacteria (Propionibacterium freundenreichii subsp. shermanii PS4), as well as bifidobacteria (Bifidobacterium animalis subsp. lactis Bb-12) and their selected analysis.

Commercial UHT cow milk with a fat content of 3.2%, as well as a bean drink obtained in laboratory conditions from germinated Adzuki beans (Vigna angularis var. angularis) were used to obtain the drinks. Fermentation was carried out at 30°C (for P. freundenreichii subsp. shermanii PS4 and L. lactis ATCC 11454) and at 37°C for 24 h (for B. animalis subsp. lactis Bb-12) for 24 h. The value of pH was measured during the fermentation, and the number of bacterial cells (plate method) and the content of selected B vitamins (HPLC-UV) were determined before and after the fermentation process. Two independent experiments were performed and each analysis was performed in duplicate

The highest increase in acidity was observed for beverages fermented by L. lactis ATCC 11454 (4.10-4.29 after 24 h) or B. animalis subsp. lactis BB-12 (4.10-4.63 after 24 h), regardless of the type of the fermented matrix. On the other hand, the mixture of the studied strains turned out to be useful for the effective fermentation of both a milk drink (4.70) and a bean drink (4.16). The determined acidification curves indicate that the bean drink is a good matrix to ferment with L. lactis ATCC 11454, B. animalis subsp. lactis BB-12 or a mixture of these bacterial strains. Changes in the population of live cells of the starter bacteria were observed in all the drink samples, confirming their metabolic activity. The greatest changes in the population were recorded in drinks fermented by a mixture of strains - 7.35 log(cfu/ml) before fermentation, as well as 7.93 log(cfu/ml) and 7.87 log(cfu/ml) after fermentation of milk and bean drinks, respectively. The research proved the possibility of using lactic acid fermentation and propionic acid fermentation in the production of fermented drinks, not only fermented milk, but also fermented drink obtained from germinated Adzuki beans. The tested starter cultures, both in the form of monocultures and a starter mixture, were able to ferment the milk and plant matrix well, maintaining the viability of bacterial cells, but without significantly increasing the content of substances showing the activity of B vitamins other than cyanocobalamin.