Structural and physicochemical properties of heat moisture treated and citric acid modified acha and iburu starches

Abstract

Starches extracted from acha (Digitaria exilis) and iburu (Digitalia iburua) were subjected to heat moisture treatment and citric acid modification. Successful applications of the treatments are expected to promote commercial utilization of the starches from these underutilized crops and improve the economy and livelihood of stakeholders along their value chains. Granules of the starches from the two cereal grains were polyhedral in shape. Generally, modifications led to the clustering of the polyhedral of the starches granules. Indentations were observed on the surfaces of citric acid modified (CAM) starches. This could be due to the weathering effect of acid hydrolysis. Modification methods employed did not affect the characteristic type-A crystal polymorph of the native starches. The starches generally exhibited single prominent peaks at (2ϴ) 16 and 24, and a doublet at 17-19. Crystallinity index of the starches ranged from 27.01-27.84% for acha and 29.01–30.47% for iburu. FTIR analysis and high peak gelatinization temperatures of the starches suggested heterogeneity in the matrices. CAM starches of the two grains remained in liquid form throughout the pasting cycle. Acha starches are lighter and whiter in color. All the starch samples exhibited promising functional properties that could place them as good materials for different industrial uses. Results of this study further exposed the potentials of acha and iburu starches for food and pharmaceutical applications.