Utilization of exopolysaccharide producing lactic acid bacteria to ameliorate the physicochemical, textural, and sensory attributes of low-fat yogurt enriched with phytosterols

Low-fat yogurts are commonly characterized as having weak texture. Besides, enrichment of yogurt using phytosterols unfavorably reduces the textural quality. The core objective of the current study was to investigate the effects of using Leuconostoc mesenteroides and Lactococcus lactis to improve the quality of phytosterols-enriched yogurt. The optimization of dextran production in yogurt by Leuconostoc mesenteroides was assessed via response surface methodology using a four-factor five-level central composite design. The independent factors were fermentation time (۱۵-۳۵ min), fermentation temperature (۲۰-۴۰œC), Leuconostoc mesenteroides to Lactococcus lactis inoculation ratio (۱۰:۹۰-۹۰:۱۰), and sucrose content (۰-۶%). Results demonstrated that ۲۵œC, ۲۰ hours, ۴.۵% sucrose, and inoculation ratio of ۵۰:۵۰ provided the optimum conditions for dextran production. Fermentation temperature and sucrose content had the highest effect on dextran production; however, increasing the sucrose level decreased sensorial desirability. Producing dextran augmented the viscosity and diminished the phase separation of yogurt. Moreover, texture analysis revealed that the application of exopolysaccharide producing lactic acid bacteria compensated the opposing effects of the phytosterols and therefore, improved the hardness, adhesiveness, cohesiveness, and gumminess of the yogurt. In conclusion, data obtained herein revealed that dextran could play a promising role in the improvement of the overall quality of yogurt enriched with phytosterols.