PROTEIN-COMPOSITION AND FUNCTIONALITY OF HIGH-PROTEIN OAT FLOUR DERIVED FROM INTEGRATED STARCH-ETHANOL PROCESS

High-protein oat flour containing approximately 50% protein was derive d as a by-product from an oat starch process integrated with ethanol p roduction. The protein composition of the by-product was characterized in comparison to that of oat groats, the raw material of the process, to evaluate alterations occurring during processing. The proteins wer e fractionated according to their solubility. Amino acids of the fract ions were analyzed as 9-fluorenylmethyl chloroformate derivatives by h igh-performance liquid chromatography, and molecular weight distributi on was analyzed by sodium dodecyl sulfate polyacrylamide gel electroph oresis. In addition, functionality (in terms of protein solubility, wa ter absorption, and emulsifying capacity) of the high-protein oat flou r was compared with that of a commercial soy concentrate at a pH range of 3.0-7.0. Processing caused changes in the proportion of salt-solub le and alkali-soluble but not in the proportion of water-soluble or al cohol-soluble fractions. In oat groats, the alkali-soluble fraction ac counted for 52% of the total nitrogen, and the salt-soluble fraction a ccounted for 28%. In high-protein oat flour, almost 80% of nitrogen wa s collected in the alkali-soluble fraction; the salt-soluble fraction accounted for <3% of the total nitrogen. The amino acid composition an d molecular weight distribution of the protein fractions were not seve rly altered during processing. Solubility and emulsifying properties o f the high-protein oat flour were competitive with those of the soy co ncentrate. Commericial soy concentrate, however, absorbed three to fou r times more water than did the oat flour over the pH range studied.