Aqueous extraction and functionality of protein concentrates manufactured from cold press meals of pumpkin, pomegranate, and grape seeds

Abstract

Purpose: Oil processing generates an increasing extent of deoiled seed meals globally, which are rich in plant proteins. Based on simple aqueous extraction techniques, a variety of technically and biologically active plant protein products can be generated from deoiled meals. Methods: Pumpkin, pomegranate, and grape seed protein concentrates were prepared using aqueous protein extraction techniques (alkali extraction-isoelectric precipitation (AE-IP), salt extraction (SE), and micellar precipitation (MP)). Protein concentration was determined using a Kjeldahl method. SDS-PAGE was utilized to determine the molecular weight distribution of proteins. Functional characteristics of the isolated proteins were investigated based on solubility, water and oil holding capacities (WHC and OHC), foaming and emulsion forming capacities, drop shape tensiometry, and thermal gelation characteristics. Results: Protein concentration in the samples was widely distributed between 20 and 86%. Protein contents of AE-IP-treated pumpkin, pomegranate, and grape seed protein concentrates were 82.9, 45.8, and 30.1%, respectively. Although the foam formation and water holding capacities of these protein concentrates were relatively weak, oil holding characteristics were comparable or better than a commercial soy protein isolate. All proteins demonstrated considerable surface activity at the air-water interface. Pumpkin and pomegranate protein concentrates formed weak gels upon heating, whereas the heating of grape seed protein concentrates did not yield thermally induced gels. Conclusion: Extraction techniques had a clear bearing on both protein concentration and functionality of the current concentrates. While further processing could enhance their functionality, current samples demonstrated considerable functionality after simple extraction techniques that are conveniently adaptable to industrial settings. © 2020, Springer Nature Switzerland AG.