The Effects of Leuconostoc mesenteroides RSG7 Exopolysaccharide on the Physicochemical Properties and Flavor Compounds of Set Yoghurt

Leuconostoc mesenteroides RSG7 was previously isolated from pepino, and its exopolysaccharide has potential bioactivities. To better understand the function of RSG7 exopolysaccharide (RE), its effects on the stability and flavour characteristics of set yoghurt were comprehensively investigated. RE was incorporated into milk at 0% (control), 0.05%, 0.10%, and 0.15% (w/v), respectively. Subsequently, samples were fermented and stored at 4 °C for 24 h. The pH, water-holding capacity (WHC), texture profiles, rheological properties, microstructure, and flavour characteristics were analyzed. The results showed that the addition of RE significantly enhanced the WHC; improved hardness, gumminess, chewiness, springiness, adhesiveness, apparent viscosity, and storage modulus (G′) and loss modulus (G″); and reduced the cohesiveness and loss tangent (tan δ) of set yoghurt in a dose-dependent manner, which might be attributed to the interaction between RE and proteins based on the compact microstructure. These results suggested that RE endowed yoghurt with better gel properties and more stability. No differences were observed in the pH of set yoghurt, while RE significantly improved flavour characteristics such as sourness, according to an electronic nose and tongue and gas chromatography–mass spectrometry analyses. Consequently, our results suggest that the bioactive properties, such as its interaction with milk proteins and flavour modulation capabilities, make it a promising functional ingredient for designing yoghurt formulations with enhanced texture, stability, and sensory profiles. This study deepens the understanding of RE functions and shows potential applications in the dairy industry.