Use of air classification technology to produce protein-enriched barley ingredients

Air classification of an industrial barley endosperm fraction with initial protein content of 8.3% mixed with Aerosil 200F flow aid resulted in protein enrichment up to 28.3% with 21.7% protein separation efficiency. By reducing the classifier wheel speed from 21500 rpm to 8000 rpm, the protein separation efficiency increased to 59.4%, whereas the protein content only decreased to 22.3%. Microstructural analysis showed that small starch granules separated together with protein in the fine fraction and had more continuous protein matrix around them. The protein-enriched fraction obtained at 8000 rpm classifier wheel speed had limited protein solubility of 9.3% at native pH 5.1. Solubility increased in acidic (pH 3, 19.6%) and especially in alkaline (pH 11, 91.9%) conditions. Protein fraction had water and oil binding capacities of 1.2 and 1.1 g/g, respectively. Foaming properties tested at different pH-values revealed best capacity at pH 3. Thermograms showed two melting temperatures, varying from 60.0 to 64.2 'C and from 90.5 to 95.5 'C for all the studied fractions. Cereal side-streams such as the industrial barley endosperm fraction can be utilised as potential plant protein ingredient for various food/feed applications. However, further studies are needed to evaluate the technological, nutritional, and sensory characteristics of this protein enriched fraction.