Upcycling seaweed residues via comparative pretreatment evaluation to develop functional protein ingredients for soy-based high-moisture meat analogs

Growing environmental concerns and demand for sustainable diets are driving interest in alternative proteins for plant-based meat analogs. Seaweeds are an attractive option due to their high protein and nutrient content, but their tough cell walls make protein extraction challenging. Upcycled seaweed residues (USR) offer a sustainable solution for developing functional protein ingredients. Therefore, this study systematically evaluates seaweed residues subjected to different pretreatments, mildly acidic extraction, autoclaving, and enzymatic hydrolysis, to develop functional protein ingredients for soy-based high-moisture meat analogs. Among these, enzymatic hydrolysis significantly enhances the protein purity and solubility while reducing the water holding capacity and surface charge stability. When incorporated into Soy Protein Isolate (SPI) blends, USR alters the gelation behavior and enhances the gel strength and hardness owing to thermally induced polysaccharide–protein interactions. However, higher USR concentrations (≥15 %) compromise structural anisotropy, as indicated by lower texturization indices, disrupted fibrous structures, and an increased proportion of random coil structures. Chemical analysis further reveals weakened hydrogen bonds, disulfide bonds, and hydrophobic interactions at elevated USR levels, highlighting the adverse effects of excessive USR incorporation on protein network formation. Consequently, moderate inclusion (≤10 %) of USR proves optimal, achieving a balance between improved mechanical properties and desirable fibrous texture. These findings highlight the potential of enzymatically treated USR as a sustainable and functional protein-rich ingredient in advanced plant-based meat analog formulations.