Effect of compositional interaction on in vitro digestion of starch during the milling process of quinoa

With the gradual stripping of cellulose and protein in the milling process, the proportion of starch gradually increased to 91.35 %. In particular, milling reduced the content of saponins from 5.06% to 0.23%. Milling increased the swelling power of quinoa flour but decreased the gelatinization enthalpy of quinoa starch. Accordingly, the microstructure of quinoa with higher milling degree after cooking was more uniform and denser. Fourier transform infrared (FTIR) analysis showed that starch-protein interaction was beneficial to protect the ordered structure of quinoa starch. The digestibility of protein and starch was interrelated, and the digestibility rate increased with the raising milling degree. By fitting the starch digestograms and combining the digestion kinetic model, three digestion patterns of quinoa starch during milling were determined. The results of the confocal laser scanning microscope showed that the physical barrier composed of protein matrix coated starch and starch-protein complex affected starch digestion.