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.

Keywords:
waxy rice starch; phosphorylation; lactylation; dual-modified