Effects of Chemical and Enzymatic Modifications on Starch-Stearic Acid Complex Formation

Debranched unacetylated and acetylated potato starches with two degrees of substitution, 0.041 (low) and 0.078 (high), combined with or without beta-amylase hydrolysis were prepared to form soluble and insoluble complexes with stearic acid. The effects of modifications on the complexation, thermal properties, and X-ray patterns of soluble and insoluble complexes were investigated. Acetylation decreased the recovery of insoluble complexes but increased that of soluble complexes. Low acetylated, beta-amylase-treated starch had a significantly increased amount of complexed stearic acid (123.1 mg/g) for insoluble complexes; high acetylated, beta-amylase-treated starch had the highest complexed stearic acid (61.2 mg/g) for the soluble complexes. The melting temperature of the complexes decreased with acetylation. All beta-amylase-treated acetylated complexes displayed the V-type diffraction pattern with peaks at 2 theta = 7.4 degrees, 12.9 degrees, and 20 degrees. These results suggest that starch can be modified by acetylation, debranching, and/or) beta-amylase to produce significant quantities of soluble starch-stearic acid complexes.