Stabilization of Omega-3-Rich Emulsions Using Bio-Based Ingredients Recovered from Pomace and Microalgal Side-Streams

Agro-industrial by-products, such as olive and grape pomace, are potential sources of phenolic antioxidants, while spent microalgal biomasses offer functional biopolymers. These matrices could replace synthetic additives in stabilizing omega-3-rich lipid systems which are highly susceptible to oxidation. In this doctoral research natural antioxidant and emulsifying compounds obtained from these sources were assayed in order to stabilize oil-in-water emulsions containing flaxseed oil, a model omega-3 fatty acids-rich oil. First, a green extraction process for wet olive pomace was optimized using response surface methodology, while grape pomace phenolics were obtained through an established aqueous-ethanol extraction. A storage stability of the olive extract was assessed, showing that freezing better preserves hydroxytyrosol levels. Second, the antioxidant performance of both extracts was evaluated in flaxseed oil emulsions; results showed a significant delay in lipid oxidation and preservation of alpha-linolenic acid, with olive phenolics exhibiting dose-dependent efficacy. Third, a protein–polysaccharide fraction extracted from spent Chlorella spp. biomass was characterized as a bio-based emulsifier with intrinsic antioxidant properties. Finally, a spray-drying microencapsulation process was developed for flaxseed oil, where olive pomace phenolics were incorporated to delay lipid oxidation. Under accelerated storage conditions, the addition of these antioxidants markedly mitigated oxidative degradation in a dose-dependent manner. These findings demonstrate that, under the tested conditions, specific extracts from olive and grape pomace, combined with microalgal biopolymers, can effectively stabilize omega-3-rich systems. This work provides a sustainable framework for the development of clean-label functional foods within a circular bioeconomy.