Glucono-δ-lactone induced Auricularia auricula polysaccharide-casein composite gels for curcumin loading and delivery

Polysaccharides could be used to form the network structure of casein (CA) gel, and affect its gelling properties. Auricularia auricula polysaccharide (AAP) has good gel properties and activity, however, how the AAP affects gelling properties of CA gels remains unclear. In this study, AAP and CA were acid-induced by glucono-δ-lactone (GDL) to prepare composite gels for curcumin loading. The effects of different AAP additions on the gel structure were emphasized. Water holding capacity, rheology, texture profile analysis, sulfhydryl content, surface hydrophobicity and gel microstructure showed that the composite gels were most structurally stable upon addition of 0.4 % AAP. The composite gels exhibited a higher strength and a more regular network structure compared to the CA gels. The results of turbidity studies showed that CA and AAP formed gels through electrostatic interactions due to pH < pI. The results of FT-IR, X-ray diffraction, fluorescence spectroscopy, and UV-Vis spectroscopy indicated that curcumin interacted with the CA and was successfully encapsulated within the gel. In addition, in vitro simulated digestion experiments demonstrated that the composite gels exhibited better protection against curcumin than the single CA gel. The results suggested that composite gels can be used as a curcumin carrier, which may enhance its wider application in the food and health industries.