Impact of ultrasound-assisted enzymatic extraction on the structural and functional properties of Tremella fuciformis polysaccharide and its application in almond-based milk

Ultrasound, when combined with enzymatic hydrolysis, distinctly influences the macromolecular structure of Tremella fuciformis polysaccharide, yielding a polysaccharide with improved functional properties. To comprehensively evaluate these attributes and validate its practical relevance, three polysaccharide samples were systematically compared: those produced by ultrasound-assisted enzymatic extraction (UAEP), ultrasound-alone extraction (UEP), and enzyme-alone extraction (EEP). It was found that UAEP exhibited significantly higher yield (1.5- and 2.5-fold greater than UEP and EEP, respectively) while concurrently reducing the weight-average molecular weight to 955 kDa, notably lower than UEP (1070 kDa) and EEP (1770 kDa). Structural analyses revealed that UAEP possessed a more porous and looser microstructure, although its monosaccharide composition and triple-helix conformation remained similar to other samples. Functionally, UAEP exhibited markedly higher emulsifying stability alongside lower apparent viscosity and superior thermal stability. Rheological characterization confirmed its pseudoplastic shear-thinning behavior with distinct viscoelasticity. Multivariate statistical analyses, including principal component analysis and correlation analysis, quantitatively established that key structural parameters, particularly molecular weight, protein and uronic acid content, were closely linked to its enhanced emulsifying performance. To validate its practical utility, UAEP was successfully incorporated into almond-based milk, where it achieved significantly enhanced physical stability (25.11%) and textural properties (consistency: 55.81 g·sec, cohesiveness: -9.84 g) comparable to a commercial walnut protein-based milk (physical stability: 12.38%, consistency: 56.22 g·sec, cohesiveness: -10.09 g). These findings demonstrate that ultrasound-assisted enzymatic extraction not only improves polysaccharide yield but also modulates its macromolecular structure, offering a viable approach to obtain multifunctional hydrocolloids for plant-based food applications.