Study of amyloglucosidase hydrolysis on the multiscale structures of normal corn and waxy rice starch and its application on acidified milk gel

Abstract

Today, there is increasing interest in the usages of porous starch in food, cosmetics and pharmaceutical applications. Normal corn and waxy rice starch were amyloglucosidase digested and thermally treated at 50 °C up to 24h. The impact of enzyme (amyloglucosidase) digestion on the multiscale supramolecular structures of normal corn and waxy rice starches were studied by using different techniques, such as scattering methods (USANS and SAXS), microscopy methods (SEM) and light scattering methods (particle size). Under enzymatic digestion, a maximum weight loss of approximately 70% was observed for starch granules from normal corn starch and waxy rice starch. A particle size study indicated that swelling occurred for both thermally treated normal corn and waxy rice starch. With enzymatic treatment, no change in the enzymatically digested normal corn starch was observed, but reduced particle size of the enzymatically digested waxy rice due to enzymatic degradation was found. USANS was able to quantify the surface roughness of starch granules by the surface dimensions, which indicated increased roughness with increasing enzyme digestion time. USANS also quantified the shape and size of pores on the surface of starch granules. With the combined SEM technique, the pores were found to become greater in size and more polydisperse as the digestion time increased. In addition, SAXS demonstrated a gradually decreased lamellar peak area for both enzymatically digested and thermally treated starches.