Presence of beta-amylase in ramie leaf and its anti-staling effect on rice cake

Abstract

Presence of beta-amylase in ramie leaf and its anti-staling effect on starch-based foods were assessed. The ammonium sulfate fractionate (80% saturation) of the ramie leaf extracts showed a beta-amylase activity, giving maltose (Glc2) as a major product, exclusively, when incubating with maltopentaose (Glc5) or soluble starch at 45A degrees C, pH 6.0. The starch-based food product (rice cake) prepared with freeze-dried ramie leaf enzyme revealed that the linear maltooligosaccharides ranging from Glc2 to Glc6 significantly increased and the shorter branch chains (DP < 15) of amylopectin increased whereas the longer branch chains (DP > 16) decreased in the product. These results demonstrated that maltosyl residue was released from the non-reducing end of the longer branch chains of amylopectin by beta-amylase. The ramie leaf-treatment sample significantly reduced the retrogradation rate during 48 h storage at 4A degrees C. As an alternative plant-origin enzyme, the ramie leaf beta-amylase has potential for a novel anti-staling additive.