Seaweed, Used as a Water-Retaining Agent, Improved the Water Distribution and Myofibrillar Protein Properties of Plant-Based Yak Meat Burgers Before and After Freeze–Thaw Cycles

This study investigated quality changes in seaweed-yak patties before and after freeze-thaw by varying seaweed addition levels (10-70%). Macroscopically, the effects on water-holding capacity, textural properties, and oxidative indices of restructured yak patties were evaluated. Microscopically, the impact of seaweed-derived bioactive ingredients on patty microstructure and myofibrillar protein characteristics was examined. LF-NMR and MRI showed that 40% seaweed addition most effectively restricted water migration, reduced thawing loss, and preserved immobilized water content. Texture profile analysis (TPA) revealed that moderate seaweed levels (30-40%) enhanced springiness and minimized post-thaw hardness increases. SEM confirmed that algal polysaccharides formed a denser protective network around the muscle fibers. Lipid oxidation (MDA), free-radical measurements, and non-targeted metabolomics revealed a significant reduction in oxidative damage at 40% seaweed addition, correlating with increased total phenolic content. Protein analyses (particle size, zeta potential, hydrophobicity, and SDS-PAGE) demonstrated a cryoprotective effect of seaweed on myofibrillar proteins, reducing aggregation and denaturation. These findings suggest that approximately 40% seaweed addition can improve the physicochemical stability and antioxidant capacity of frozen seaweed-yak meat products. This work thus identifies the optimal seaweed addition level for enhancing freeze-thaw stability and functional quality, offering practical guidance for the development of healthier, high-value restructured meat products.