Influence of enzymatic hydrolysis on the properties of red rice starch

Starch is a technologically challenging polysaccharide that arouses the global interest in its modification to increase its applicability. Thus, the objective of the present work was to study the influence of enzymatic modification on the properties of red rice starch. The enzymatic modification was performed sequentially through the actions of α-amylase enzymes and amyloglucosidase using a design of experiments where several process conditions were used at sub-gelatinization temperatures. Then the native and modified starches were characterized for its physicochemical, physical, centesimal, phytochemical, morphological, and thermal properties. The enzymatic hydrolysis of the starch granules with α-amylase resulted in 4.46% hydrolysis and more 8.63% after the action amyloglucosidase. Results revealed that surface adsorption is more limiting than diffusion. The enzymatic hydrolysis process resulted in a reduction of the amylase and amylopectin content, as well as on all phytochemicals. After hydrolysis, granules starches presented surface alterations and tendency to become spherical. Small differences on crystallinity revealed that the enzymes had more influence on the amorphous fractions of the starch granules. •Un-treated red rice starch was sequentially hydrolyzed using a-amylase and then amyloglucosidase.•Enzyme adsorption revealed to be the limiting step of the hydrolysis process.•Starch granules surface and geometry were altered after both hydrolysis.•Minor changes on gelatinization temperature and crystallinity suggest that the hydrolysis occurred on the amorphous fraction.