Effect of arabinoxylan amount and molecular structure on the microstructure, physicochemical and delivery properties of casein/arabinoxylan composite hydrogels

In this study, arabinoxylans (AXs) with different molecular structures were first extracted from corn brans using different concentrations of NaOH (0.25, 0.5, 0.75 and 1 M). AX extracted with 0.25 M NaOH (AX-0.25 M) had the highest ferulic acid content of 5.11 mg/g and AX extracted with 1 M NaOH (AX-1 M) had the lowest arabinose to xylose ratio of 0.47. Meanwhile, the molecular structure of AX and its addition amount both had an influence on the microstructure and physicochemical properties of dual-induced casein/arabinoxylan composite hydrogels (CAS/AX hydrogels) by laccase and glucono-δ-lactone. With CAS/AX mass ratio of 16:1, CAS/AX-0.25 M and CAS/AX-1 M hydrogels exhibited stronger gel strength, better water holding capacity, higher hardness, gumminess and epigallocatechin gallate (EGCG) loading capacity, which was possibly due to their stronger covalent and non-covalent interactions, and denser network microstructures. Besides, the EGCG-loaded CAS/AX-0.25 M hydrogel with CAS/AX mass ratio of 16:1 showed the lowest EGCG cumulative release percentage in 2 h of simulated gastric fluid (31.56%) and 4 h of simulated intestinal fluid (52.94%), while almost all the remaining EGCG (46.57%) was fast released in simulated colonic fluid, showing the most optimum colon-targeted release behavior and protection of EGCG at low pH and protease degradation conditions.