Effects of ultrafine grinding and cellulase hydrolysis treatment on physicochemical and rheological properties of oat (Avena nuda L.) β-glucans

In order to improve the functionality of oat (Avena nuda L.) beta-glucans and widen their applications in food industry, the oat bran was processed by ultrafine grinding and enzymatic hydrolysis, and extracted to obtain oat beta-glucans. The extracted oat beta-glucans were characterized by the molecular weight distribution, particle size, rheological properties, thermal stability, solubility and water holding capacity, and morphological properties. The average molecular weight of raw oat beta-glucans (OBG-1) and ultrafine ground oat beta-glucans (OBG-2) were 2.79 x 10(5) Da and 3.26 x 10(5) Da, respectively; while the average molecular weights of cellulase hydrolyzed oat beta-glucans (OBH-1 and OBH-2) significantly decreased to 1.98 x 10(5) and 1.05 x 10(5) Da. The particle size, thermal stability, solubility and water holding capacity showed significant correlation with molecular weight distribution. Both OBG-1 and OBG-2 had shear-thinning behavior, whereas OBH-1 and OBH-2 exhibited shear-thickening behavior. Scanning electron microscope observation suggested that cellulase hydrolyzed oat beta-glucans had fibrous structures with granular particles in aggregates sticking to the fibrous skeleton. Compared with raw and ultrafine ground oat beta-glucans, the partially hydrolyzed oat beta-glucans showed different rheological properties, which might be of potential use in the food industry. (C) 2015 Elsevier Ltd. All rights reserved.