Characterization and evaluation of acylated starch with different acyl groups and degrees of substitution

Corn starch was modified with acetyl, propionyl and butyryl groups at four different degrees of substitution (DS). FTIR, X-RD, TG–DTA, SEM, swelling power, solubility, water binding capacity and light transmittance techniques were used to characterize the samples. Effect of DS and acyl groups on physico-chemical properties of starch was studied. During acylation, the crystalline structure of starch got destroyed and starch surface was eroded. Acylated starch was thermally stable than native starch. Amylose content of the starch samples increased slightly after acylation. Swelling power and water binding capacity of native starch were 3.09 g/g and 89.8%, respectively. In acetylated, propionylated and butyrylated starch at low DS, these properties increased. But at high DS, these decreased to below that of native starch. Butyrylated starch at DS of 1.75 showed lower swelling power, and water binding capacity than acetylated starch at DS 2.55. Increase in DS and acyl group chain length from acetyl to butyryl group improved hydrophobic transformation of starch.