Effects of EPS-producing Leuconostoc mesenteroides XR1 on texture, rheological properties, microstructure and volatile flavor of fermented milk

Abstract

Leuconostoc mesenteroides XR1, a high-quality exopolysaccharides (EPS) producing strain, was isolated from wild Kefir grains. The effect of strain XR1 as a compound starter on yoghurt fermentation and storage was studied. The EPS content, viable counts, titratable acidity, pH, water holding capacity (WHC), texture, rheological properties, microstructure, volatile flavor compounds and sensory evaluation of yoghurts were determined. The EPS content of the yoghurt with XR1 was shown to be 1.64, 2.14, 1.37, and 1.29 times higher than those of the control group at days 1, 7, 14, and 21 of storage, respectively. The WHC, cohesiveness, gumminess, apparent viscosity and gel strength of the yoghurt containing XR1 were higher than those of the control group (P < 0.05). It is worth noting that supplementation with XR1 improved the acidification of the yoghurt. Scanning electron microscope (SEM) observation confirmed that the microstructure of the yoghurt containing XR1 had stronger compactness. Volatile substance analysis showed that after 7 days of storage, yoghurt supplemented with XR1 had an increased aroma of ketones and alkanes. In terms of texture, flavor and taste, Y-XR1 group obtained higher sensory scores (P < 0.05). These results collectively indicated that XR1 improved the quality of the yoghurt by increasing EPS production, thus reducing the use of chemical thickeners or stabilizers.