Comparative study on the structure and physicochemical of waxy rice starch by phosphorylation, lactylation and dual-modified

Abstract Waxy rice starch was modified by phosphorylation, lactylation and lactic acid-phosphorylation and its structure and thermodynamic properties were studied. Microscopy showed that phosphorylated and lactated starch granules maintained their integrity, while dual-modified starch granules exhibited partial adhesion. FTIR revealed minor spectral differences in phosphorylated starch, while a characteristic peak at 1738 cm-1 in lactated and dual-modified starch was due to C = O stretching vibration, indicating the presence of lactate groups. 31P NMR spectroscopy revealed that monostich monophosphate and distich monophosphate were the primary forms of phosphate ester in phosphorylated and dual-modified starch. 13C CP/MAS NMR spectroscopy showed the relative intensity of signals in the C2, C3, C5 and C6 regions reduced following modification. XRD showed that modification, especially dual modification, reduced starch crystallinity. The three modification methods did not change the non-Newtonian fluid properties of waxy rice starch, and they all belonged to shear-thinning systems and retained the A-type crystalline structure. The gelatinization temperature and enthalpy of modified starch decreased more than that of native waxy starch, especially dual-modified starch.