Structural and in vitro digestibility properties of esterified maca starch with citric acid and its application as an oil-in-water (O/W) pickering emulsion stabilizer

The objective of the present study was to determine structural and in-vitro digestibility properties of esterified maca starch with citric acid (EMSC) and explore its application in oil-in-water (O/W) pickering emulsion. EMSC was prepared by esterifying native maca starch (NMS) with different concentrations of citric acid (0, 10, 20, and 30%, w/w). The structural properties were characterized by SEM, FT-IR, XRD, and 13C and 1H NMR spectroscopy, which demonstrated that EMSC exhibited new ester linkages from citric acid in NMS. The in vitro digestibility results showed that EMSC had the significantly lower rapidly digestible starch contents and higher resistant starch contents compared to NMS. The properties of O/W pickering emulsion stabilized with NMS and EMSC were evaluated by microscopy, particle size, and zeta-potential. The results showed that the emulsion formed with EMSC had smaller particle size and improved stability than that formed with NMS. Therefore, EMSC could be used as source of the emulsifier or stabilizer in the food industry.