Effects of Different Prebiotics on the Gel Properties of Milk Protein and the Structural Features of Yogurt

The impact of prebiotics on the structural characteristics of yogurt is an important aspect of evaluating its functional properties. This study aimed to evaluate and compare the effects of several commonly used prebiotics, including fructooligosaccharide (FOS), galactooligosaccharide (GOS), inulin (INU), polydextrose (PDX), and xylooligosaccharide (XOS), on the gel properties of milk protein and the structural features, with respect to the texture and rheology, of stirred yogurt during and after fermentation. The results revealed that the supplementation of INU, PDX, and XOS was involved in the construction of protein networks during fermentation, promoting a viscous and more elastic gel structure, due to the enhanced protein–water interactions. This resulted in a significant increase (p < 0.05) in structural stability (higher critical strain (γ(c)) and greater thixotropy), firmness, cohesiveness, and rheology (G′ and G″) and a significant decrease (p < 0.05) in the loss of yogurt during centrifugation. Conversely, the supplementation of GOS and FOS did not appear to be involved in the construction of the protein network and barely affected the rheological properties of the gel during fermentation. However, a significant increase (p < 0.05) in viscosity and firmness, and a slight decrease (p > 0.05) in loss during centrifugation were still observed in the yogurt. These findings could be useful for a comprehensive assessment of the application potential of these prebiotics in yogurt, when combined with their respective prebiotic properties.