Solubility properties of barley flour, protein isolates and hydrolysates

Protein solubility properties of barley flours (BF), barley protein isolates (BPI) and barley protein hydrolysates (BPH) were determined as a function of pH and NaCI concentration. BPIs were produced from both hulled (BPI-1 and BPI-3) and hull-less (BPI-2 and BPI-4) barley flours. Sodium metabisulphite (BPI-1 and BPI-2) or L-cysteine (BPI-3 and BPI-4) were included in the extraction procedure. BPI-4 was hydrolyzed with Alcalase in order to produce hydrolysates of 3% (BPH-1) and 6% (BPH-2) degree of hydrolysis. Electrophoretic properties of BFs, BPIs and BPHs were examined by SDS-PAGE. The results showed that solubility properties were affected by the changes of pH and ionic strength of the medium in all samples. The solubility properties of barley proteins were especially higher in the strong acidic and basic pH regions. Solubilities of BPI-1 and BPI-2 in distilled water were lower than those of BPI-3 and BPI-4. The lowest solubility was observed around the isoelectric points of BFs and BPIs. SDS-PAGE provided significant information about the monitoring of limited protein hydrolysis that produced large quantities of low molecular weight barley protein fragments with the Alcalase treatment. The solubility properties of BPHs around the isoelectric point were increased as a result of the limited hydrolysis.