Reducing the risk of spoilage caused by Bacillus cereus in cow's and goat's milk yogurt with berries puree
2023
Cușmenco, Tatiana | Sandulachi, Elisaveta | Bulgaru, Viorica | Macari, Artur | Netreba, Natalia | Sandu, Iuliana | Dianu, Irina
The objective of this study was to investigate the impact of adding aronia (Aronia melenocarpa), raspberry (Rubus idaeus), and strawberry (Fragaria ananassa) in the form of 10% puree to a mixture of cow's and goat's milk in order to reduce the risk of spoilage caused by activity of Bacillus cereus in yoghurt made from a mixture of cow's and goat's milk. During the fermentation process (360 min.), changes in water activity, pH, moisture content, bacterial growth curve were monitored. The results showed a decrease in water activity, pH, and moisture content. Adding aronia puree to yoghurt yielded the most significant results for water activity modification (0.971-0.868), pH (5.31-4.28), moisture content (85.12-81.55 %), and optical density (0.19-0.34). Also, the investigation of the kinetics of the Bacillus cereus grows indicated that the stationary phase was reached at 360 minutes, resulting in a total population of 5.5·1013 c.f.u./g. Microscopic examination revealed Gram-positive strains of lactic acid bacteria, arranged in chains of varying lengths, in an amount of 139·102 c.f.u./g. Antimicrobial activity showed a zone of inhibition with a diameter of 18.5±0.1 mm in aronia yoghurt, a zone of inhibition with a diameter of 16.2±0.2 mm in raspberry yoghurt and a zone of inhibition with a diameter of 15.2±0.1 mm in strawberry yoghurt compared to classic yoghurt which showed a zone of inhibition with a diameter of 12.1±0.2 mm.
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