Protein concentrate extracted from grape seeds: Impact of different pH levels on the amino acid composition, structural, thermal, morphological, and functional properties [pdf]

Background.Grape seeds, a major by-product of wineries, contain a high amount of protein and could potentially be exploited as a promising source of protein concentrate.There is a growing need to extract protein from vegetable sources, as opposed to animal sources, due to growing environmental concerns.Materials and methods.The protein concentrate was prepared from defatted grape seed meal by modifying the extraction pH at four levels i.e. 8, 9, 10, and 11.The effect of different pH levels on the amino acid composition and its structural, thermal, morphological and functional properties were studied.Results.The extracted grape seed protein concentrate resulted in a maximum yield and purity value of 12.23 0.23% and 55.66 0.15%, respectively, at different pH values.With an increase in the pH of grape seed protein concentrate, an increase in solubility, foaming stability and capacity, emulsifying capacity, and water and oil holding capacity were observed.In the flow properties of grape seed protein concentrate extracted at different pH levels, significant changes were observed in the loose bulk density, packed bulk density, true density, Hausner's Ratio, Carr's Index, and angle of repose of the protein concentrate.The SEM analysis revealed that protein in the pH-adjusted samples showed a more condensed and clustered shape.The grape seed protein concentrate extracted at pH 10 exhibited greater thermal stability, with a denaturation temperature of 104.23 2C, in comparison to samples extracted at other pH levels.Conclusions.Adjusting the pH during the extraction process can be used as a promising technique to enhance the quality of grape seed protein concentrate, and has a variety of applications in various food formulations.