Ultrasound combined mechanical wall-breaking extraction of new Ganoderma leucocontextum polysaccharides and their application as a structural and functional improver in set fat-free goat yogurt production

Herein, we investigate the yield, micro-structures, rheological properties and bioactivities of new Ganoderma leucocontextum polysaccharide (GLP_UBE) obtained from Kangding via ultrasound combined mechanical wall-breaking extraction (UBE), and examine the effect of GLP_UBE as a structural and functional improver on the physicochemical, sensory, aromatic, water-holding capacity (WHC), textural, rheological, micro-structural and protein structural properties, and bioactivities of set fat-free goat yogurt (set-FGY). Through response surface optimisation, the extracted GLP_UBE achieved a maximum yield of 2.18 %, showing good apparent viscosity and elastic behaviour in 3 % aqueous solution as well as good micro-structure and significant anti-oxidant and anti-diabetic activities. The presence of 0.12 % GLP_UBE significantly improved the WHC, pH, acidity, textural and rheological properties, protein concentration and secondary structure, but had no effect on the protein primary structure in set-FGY production. The addition of 0.12 % GLP_UBE had an excellent ability in promoting sensory acceptance; total solid, and total polyphenol contents, WHC, pH, acidity, texture, free amino acid contents, viscosity, rheology and aroma properties; enhancing anti-oxidant and anti-diabetic abilities; inhibiting protein degradation; and maintaining the micro-structure and stability of the primary and secondary structures of protein complex of set-FGY during 21 days of storage. Therefore, GLP_UBE can be used as an innovative structural and functional improver in set fat-free yogurt industry.