Effect of pullulanase treatment on the structural and in vitro digestive properties of starch-ovalbumin complexes

In this study, corn starch (CS) was debranched using pullulanase (PUL) and complexed with ovalbumin (OVA) under heat-moisture-treatment (HMT) conditions to investigate the physicochemical properties, structural properties and digestibility of corn starch-ovalbumin (CSOVA) complexes with different degrees of debranching. The results showed that PUL hydrolyzed the (1 → 6)-α glycosidic bonds to produce more linear chains as debranching time progressed, and these were able to form complexes between CSOVA complexes effectively. The combination of PUL and OVA treatment significantly changed the physicochemical properties of CS, as evidenced by the reduction in viscosity and swelling of the granules. In addition, the microscopic morphology of the CSOVA complexes gradually changed from small to large aggregates. After the addition of OVA and PUL treatment for 4 h, while X-ray diffraction (XRD) showed a crystallinity shift from A-type to B + V, with relative crystallinity decreasing from 19.45 % to 14.91 %. Fourier-transform infrared (FTIR) spectroscopy confirmed altered starch-protein interactions without new chemical bonds. In vitro digestion demonstrated resistant starch (RS) content increased to 45.6 % after 4 h of debranching. This study provides scientific evidence that the corn starch treated with PUL is a better source to form CSOVA complexes, providing a valuable slow-digesting starch.