A comparative study of submicron‐ and micron‐sized rice particles: enzymatic hydrolysis in vitro and food efficiency ratio in vivo

Abstract

Hydrolysis and absorption properties of submicron-(below 1 lm) and micron-sized (over 100 lm) powders of raw rice, heat-gelatinized rice, fermented rice and wheat were investigated in vitro and in vivo. Nutrient content such as protein, carbohydrate or vitamin C in the samples was not different significantly between submicron-and micron-sized powders, but it showed difference according to processed type of the powders. Submicron-sized powders were hydrolyzed more easily than micron-sized powders by a-amylases such as industrial, human salivary and porcine pancreatic a-amylase but not by a-glucosidase in all the tested samples. Patterns of blood glucose change were investigated in rats. The highest glucose levels were obtained at 30 min after oral administration in both submicron-and micron-sized powders, but the levels were decreased drastically in groups administered submicron-sized powders, while they were slow and gradual in groups administered micron-sized powders. On the contrary, the body weight gained and food efficiency ratios showed a tendency to be decreased slightly in mice fed with submicron-sized rice powders compared to those with micron-sized rice powder.

Functional Properties of Submicron‐Scale Rice Flour Produced by Wet Media Grinding

“…We consider that the increased surface area caused by the size reduction increased the exposure to water molecules, and WAI of finer particles increased. Digestibility increased significantly in the order of HLF < HSF < JLF < JSF < MMF (Table II): as particle size decreased, the surface area exposed to the a-amylase increased, increasing digestibility (Cottrell et al 1995;Lee et al 2011). Swelling power increased in the order of HLF = HSF = JLF < JSF < MMF.…”

“…Enzymatic Digestibility. Digestibility increased significantly in the order of HLF < HSF < JLF < JSF < MMF (Table II): as particle size decreased, the surface area exposed to the a-amylase increased, increasing digestibility (Cottrell et al 1995;Lee et al 2011). HLF was prepared using a larger screen opening (2.0 mm) and had a lower degree of starch damage; HSF, on the other hand, was prepared using a smaller screen opening (1.0 mm), which induced a higher impact during pulverization and smashed the organized structure of the grain composite.…”

“…Chen et al (2010) reported that wet-milling in a media mill altered the pasting properties of corn starch; molecular degradation took place during the pulverization, and molecular weight was the dominant factor in the alteration of properties. Dry turbo-milling of raw, heat-gelatinized, and fermented rice increased the nutrient content of submicronsized rice flour, and submicron-sized powders seemed to be more easily hydrolyzed than micron-sized powders (Lee et al 2011).…”

“…The particle size heterogeneity influences the hydrolysis and hydration properties of rice flour, and further size reduction below a critical size (<80 µm fraction) strengthened effects on structural changes in grain components (de la Hera et al 2013). Dry turbo-milling of raw, heat-gelatinized, and fermented rice increased the nutrient content of submicronsized rice flour, and submicron-sized powders seemed to be more easily hydrolyzed than micron-sized powders (Lee et al 2011). Dry turbo-milling of raw, heat-gelatinized, and fermented rice increased the nutrient content of submicronsized rice flour, and submicron-sized powders seemed to be more easily hydrolyzed than micron-sized powders (Lee et al 2011).…”