Enhancing the anti-digestive properties of spray-dried resistant starch via zein coating

Spray drying is a conventional drying method for producing resistant starch particles (RSP) powder, but it may negatively affect crystallinity and anti-digestibility. To overcome this limitation, we propose a zein-coating strategy to improve the anti-digestive properties of spray-dried RSP powder. We found that zein densely adsorbed on the surface of RSP through spray drying, resulting in the formation a shell structure. The water contact angle of zein-coated RSP (Zein@RSP) was increased from 20° to 75°, rendering the semi-hydrophobic surface properties. The results of CD and XPS analysis demonstrated that the adsorption of zein on the surface of RSP is based on the hydrogen bonding and electrostatic interactions between zein and RSP, enhancing their intermolecular interactions and structural compactness. In vitro digestion experiments demonstrated that Zein@RSP exhibited significantly improved resistance to enzymatic hydrolysis, showing that the resistant starch content increased up to 82.92 % and digestibility decreased to 29.06 % through zein coating. Furthermore, enzyme activity assays indicated that zein effectively inhibited α-amylase and amyloglucosidase via non-competitive inhibition, with a maximum relative inhibition rate of 50 % and 47 %, respectively. Thus, this spray-drying-based zein coating approach to improving the anti-digestive properties of RSP, offers potential applications in functional foods and low-glycemic-index products.