Composition and Techno-functional Properties of Grape Seed Flour Protein Extracts

Defatted grape seed flour (DGSF), a byproduct of the grape seed oil production, was investigated as a potential source of protein-enriched food ingredients with functional properties. The operation conditions of the alkaline extraction followed by the acid precipitation method were studied by response surface methodology, aiming to maximize the protein extraction yield. These conditions were temperature 50 degrees C, solvent/meal ratio 1:15, pH 11, and 150 min extraction time in two sequential extraction cycles, achieving a product with 32.63 +/- 0.07\% (w/w) d.m. of protein content. A second extract with 38.17 +/- 1.34\% (w/w) d.m. of protein was obtained under the same conditions, but using an additional centrifugation step before the acid precipitation. The amino acid profile, solubility, water and oil retention capacity, and emulsifying and foaming properties of the DGSF and the obtained extracts were compared. Both extracts could be used as food ingredients with different nutritional and technological purposes.