Physical, technological and sensory parameters of yogurts are improved with Levilactobacillus brevis SD48 and Lactiplantibacillus plantarum SD30 co-cultures effect of co-cultures on yogurts

Abstract

Yogurt, a fermented dairy product known for its high acidity, pathogen destruction, and safety, has significant potential due to its positive effects on various diseases resulting from the microorganisms it contains. Therefore, the aim of this study was to to evaluate the effects of sourdough-derived Levilactobacillus brevis and Lactiplantibacillus plantarum strains when incorporated as co-cultures together with traditional yogurt starter bacteria on the survival capacity, technological characteristics, and sensory properties of yogurt samples. The findings indicated that microbiological counts in all yogurt samples decreased logarithmically during storage, while pH values remained approximately 4.10. Correspondingly, total titratable acidity (TTA) values increased throughout the storage period and exhibited a linear relationship with pH. Syneresis, which is considered a key technological quality parameter, ranged between 32.9% and 39.3%, whereas water activity values were measured between 0.914 and 0.922. In order to evaluate the viscoelastic behavior of the yogurt samples, a power law model was applied. The results demonstrated that the elastic modulus (G') of all samples showed a linear correlation with pH, and the elastic behavior of the samples was more pronounced than the viscous behavior (G' > G''). During the storage period, it was observed that the L* value of the samples mostly decreased, the yellowish color in the b* value increased, and there was no noticeable change in the a* value. The results suggested that these strains exhibit certain biological limitations in GABA production under thermophilic yogurt fermentation conditions. Furthermore, it was noted that the yogurt sample containing Levl. brevis co-culture received the highest score in sensory evaluation. Overall, the results of this study show that enriching yogurt samples with co-cultures significantly affects the functional properties of dairy products.