Ultrasound-Treated Dendrobium officinale Polysaccharides as Functional Ingredients for Plant-Based Yogurt: Enhancing Gel Properties of Soy Protein Isolate

The application of bioactive polysaccharides from medicine–food homology sources in the food industry still poses a significant challenge. This study investigated the effects of ultrasonically modified polysaccharides from Dendrobium officinale on the physicochemical properties of plant-based yogurt. The Dendrobium officinale polysaccharides were treated with ultrasound at varying power levels (200–600 W) and durations (20–40 min). The modified polysaccharides (0.5%) were then incorporated into soy-protein-isolate-based (5%) yogurt, and the resulting composites were characterized in terms of their structural and functional properties. Results showed that optimal treatment (400 W, 20 min) reduced the particle size of the polysaccharides while enhancing their hydrophilicity and hydroxyl group exposure. The incorporation of these modified polysaccharides into SPI gels promoted probiotic growth, lowered the gel pH, and facilitated the formation of protein gel. Consequently, the resulting gels exhibited a denser microstructure, along with superior gel strength, water-holding capacity, apparent viscosity, storage modulus, deformation resistance, and antioxidant activity (scavenging DPPH and ABTS radicals). These findings suggest that ultrasonic treatment not only modifies polysaccharides from Dendrobium officinale to enhance their bioactivity but also augments their capacity to facilitate protein gel formation. This work provides the evidence that ultrasound-modified polysaccharides from Dendrobium officinale can simultaneously act as prebiotic stimulators and structural reinforcements, offering a novel strategy for designing high-quality plant-based yogurts.