Effect of different pressure treatment on preparation of wheat starch acetate and their structure characterization

Wheat starch suspensions(40%) were high-pressure-homogenized at increasing pressures of 0,20,40,60,80 MPa,followed by esterification with acetic oxide,respectively. Then,FTIR,PLM,XRD and SEM were carried out on wheat starch acetates morphology and structure analysis. The results indicated that ester carbonyl was introduced into starch molecules after esterification. High pressure improved esterification degree of wheat starch significantly,and DS increased by 47.70% when compared with unhighpressured starch. The highest substitution degree of 0.096 was achieved at 40 MPa. From polarization diagram,the umbilical point of starch particles burst and the crack expand outward from the umbilical point with the increasing pressure.Birefringence almost disappeared when it arrived at 80 MPa. A type crystal structure of wheat starch couldn't be transformed by high-pressure homogenization and low esterification,however,the pressure tended to disrupt granule crystallinity structure. Starch acetate particle hold the samed morphology with native wheat starch,but microshear deformation and mechanical folding developed on starch granules of 20 MPa. Under the 80 MPa,starch granule surface appeared serious mechanical damage and crack,and some of the relatively large starch granular disintegrated even adhered with each other,which was one of reasons why the substitution reduced.