Effects of concentration and partial hydrolysis on functional properties of hull-less barley protein concentrates

Abstract

Effects of protein concentration and partial hydrolysis on protein solubility (PS), foaming properties and water holding and oil absorption capacities of hull-less barley protein concentrate (HBPC) were investigated in this research. Defatted hull-less barley flour (dHBF) was used for the production of HBPCs which were prepared using different extraction methods. HBPC-1 was extracted from dHBF using 0.15 M NaCl at pH 9 according to flour to solvent ratio of 1:10 and an isoelectric precipitation was applied at pH 5. HBPC-2 was extracted from dHBF using 0.06 M NaOH at pH 11.2 with flour to solvent ratio of 1:20 and an isoelectric precipitation was applied at pH 5.4. HBPC-1 and HBPC-2 were applied to partial-enzyme hydrolysis with subtilisin A for producing barley protein hydrolysates. SDS-PAGE images of dHBF, HBPCs and hydrolysates were also studied to monitor the extracted and hydrolysed proteins. PS properties of HBPCs were not significantly influenced by increasing protein concentration, while the pH of the medium significantly influenced this property. The PS properties of hydrolysates at pH 6 increased as a result of the partial hydrolysis. The soluble proteins of HBPC-1 exhibited better foaming ability at all protein concentrations and pH environments. In addition, the soluble proteins of the HBPC-2 presented a better foam stability. Foaming properties were influenced by partial hydrolysis. The partial-enzyme hydrolysis did not improve the foaming properties of concentrates.