Ultrasound-Extracted Red Grape Seed Protein as a Partial Egg Replacer in Cake Formulation

Egg yolk is a key multifunctional ingredient in cakes, contributing to structure, emulsification, foaming, and color, but its replacement with plant-based proteins is increasingly explored due to sustainability, health, and dietary considerations. This study aims to develop an alternative protein concentrate from red grape seed meal and evaluate its potential as a partial egg replacer in cake production. Red grape seed protein concentrates (GSPs) were produced using conventional alkaline extraction (AE) (pH 10, 15 min) and ultrasound-assisted alkaline extraction (UAE) (80% amplitude, pH 10, 15 min) and subsequently characterized for protein recovery, water- and oil-binding capacities (WBC and OBC), molecular weight distribution, and structural properties. UAE yielded a higher protein recovery (8.2%) compared to AE (6.7%), while also improving WBC (3.36 ± 0.05 g/g) and OBC (6.49 ± 0.01 g/g). The protein content of both concentrates exceeded 50% (GSP-AE: 53.48%; GSP-UAE: 54.37%). SDS-PAGE revealed no major changes in molecular weight distribution but showed increased band intensity by UAE, suggesting enhanced protein recovery and extractability. FTIR analysis indicated ultrasound-induced conformational modifications, while SEM images revealed smaller and more porous protein particles, which collectively contributed to the improved functional properties of GSP-UAE. Therefore, the UAE-derived protein concentrate (GSP-UAE) was incorporated into cake formulations at 10% and 20% egg yolk replacement levels. Cake quality was evaluated by physical, textural, color, and antioxidant properties. Cakes with 10% substitution showed similar height and hardness to the control, indicating comparable structural quality. At 20% substitution, cakes became harder and more compact, with more pronounced color changes. Antioxidant activity increased dose-dependently up to 375.25 µg Trolox/g. Overall, the results demonstrate that UAE improves the functionality of GSP and that lower incorporation level enables partial egg yolk replacement without compromising cake quality, while simultaneously enhancing the nutritional and functional value of the product. PRACTICAL APPLICATIONS: This study shows that protein extracted from red grape seed pomace using ultrasound can be used as a functional, plant-based ingredient to partially replace egg yolk in cake formulations. At moderate substitution levels, cake quality is maintained while antioxidant content is increased. This approach offers bakeries and food manufacturers a practical way to reduce egg usage and valorize grape processing by-products in more sustainable bakery products.