Enzyme Resistant Dextrins from High Amylose Corn Mutant Starches

Abstract

This work was undertaken to investigate the effects of amylose content and chemical modification on enzyme resistant dextrin content of high amylose corn mutant dextrins. Dextrins made from high amylose corn mutant starches, including dull sugary 2 (du su2), amylomaize V, amylose extender dull (ae du), amylomaize VII, and chemically modified amylomaize V and VII, were characterized for moisture, solubility, reducing sugars, and enzyme resistant dextrin contents after dextrinization. Moisture content decreased, whereas soluble and reducing sugar contents rose rapidly in the first 60 min of conversion. Reducing sugar content began to decrease after 60 min of reaction, which corresponded to the onset of a rapid increase in enzyme resistant dextrin content. The enzyme resistant component in dextrin was not detected until fragments of low molecular-weight saccharides were produced by hydrolysis. These fragments recombined into randomly branched molecules that were resistant to enzymatic digestion. One proposed mechanism contributing to the lower enzyme resistant dextrin content of chemically modified high amylose corn dextrins is that the introduction of modifying groups to starch presented a steric hindrance for transglucosidation and repolymerization reactions during dextrinization, consequently resulting in lower enzyme resistant dextrin content.