Effect of protein content, salt concentration and enzyme hydrlysis on some functional properties of hull-less barley protein concentrate

In this study, some functional properties (protein solubility, emulsifying and foaming properties) of hull-less barley protein concentrates (HBPC-1 and HBPC-2) produced at different extraction pHs (pH 9 and pH 11.2, respectively) were investigated. Effects of protein contents (%0.25, 0.5, 1.0 (w/v)), salt concentration (0.1 M and 0.25 M NaCI at 0.25% concentration) and degree of enzyme hyrolysis on some functional properties of HBPC-1 and HBPC-2 were studied as a function of pH (2-10). Barley protein hydrolysates (BPH) having 2% and 5% degree of hydrolysis were prepared from HBPC-1 (BPH-1 and BPH-2, respectively) and HBPC-2 (BPH-3 and BPH-4, respectively). Functional properties of hydrolysates were investigated in distilled water and 0.25 M NaCI at 0.25% protein concentration. Protein contents of HBPC-1 and HBPC-2 were 70.6% and 90.7% on dry weight basis, respectively. Protein solubility values (%) of HBPC-1 were higher at all protein concentrations than that of HBPC-2 in distilled water. Generally, at all pHs, the emulsifying properties of HBPC-1 were higher than that of the HBPC-2. In distilled water, the foam volumes (FV, cm3) of HBPC-1 at 0.5% (w/v) concentration were the highest at all pHs, besides the foam half-lifes (FHL, min) of HBPC-2 were the highest at all protein concentrations and pHs. The emulsion and foaming properties of HBPC-1 and HBPC-2 in distilled water were the lowest at pH 6. The protein solubility values in salt solutions decreased according to the values obtained in distilled water. The protein solubility values of HBPC-1 were higher in salt solutions than that of the HBPC-2. The emulsifying properties of HBPC-1 were higher in salt solutions than that of the HBPC-2. Generally, among the salt solutions, the highest FV and FHL values were obtained with the soluble proteins of HBPC-1 in 0.1 M NaCI solution at 0.25% protein concentration. The protein solubility values of the hydrolysates of HBPC-1 and HBPC-2 increased in distilled water and salt solution. The highest protein solubility in salt solution and distilled water were obtained with the hydrolysates of BPH-1 and BPH-2, respectively. The emulsifying properties of all hydrolysates decreased in both solutions. The foaming properties of hydrolysates were influenced from the ionic strength of the media; as FHL values of the hydrolysates increased in salt solution, FV values were affected negatively. Key words: Hull-less Barley; Protein Concentrate; Functional Properties; Protein Solubility; Emulsion Properties; Foaming Properties; Enzyme Hydrolysis.