Emulsifying and foaming properties of sunflower protein derivatives

The results of a study carried out to evaluate the dependence of the emulsifying and foaming properties of sunflower protein derivatives on pH, ionic strength, and heat denaturation are reported. Sunflower meal and concentrate emulsifying activity is pH-dependent and has a minimum close to the isoelectric point corresponding to a minimum protein solubility. The addition of salt strongly affects the protein solubility and emulsifying activity of the products, which increase even at the isoelectric point. The effect of salt on protein solubility and emulsifying activity of the heat-denatured products is otherwise-nil. The foaming properties of the meal and concentrate are also pH-dependent with minimum values which differ for the untreated (pH 4.0) and for the heat-treated products (pH 6.0-6.5). Salt addition substantially improves the foaming properties of the products and, unlike the emulsifying properties, the addition of salt is effective even with the heat-treated products. Comparing the emulsifying and foaming properties it may be inferred that a mild denaturation depresses the emulsifying properties of sunflower protein while it does not affect, or actually improves, its foaming capacity.