Improving the Quality of Unwashed Spanish Mackerel (Scomber japonicus) Surimi Using Psyllium Husk Powder: Effects on...

The gelation characteristics of surimi are a key determinant of the quality and functional performance of surimi-based products. This study examined how psyllium husk powder (PHP) modulates the gelation behavior, structural properties, and molecular interactions of myofibrillar protein (MP) extracted from unwashed surimi. Surimi gel and MP composites containing different PHP levels were evaluated using texture profile analysis, water-holding capacity, low-field nuclear magnetic resonance, differential scanning calorimetry, particle size distribution, turbidity and solubility assays, Fourier transform infrared spectroscopy, ultraviolet absorption spectroscopy, and scanning electron microscopy. PHP addition noticeably enhanced the structural integrity and water retention of surimi gels, resulting in denser and more cohesive networks with reduced cooking loss. Water mobility shifted toward more tightly bound states, accompanied by improved thermal stability. PHP promoted protein aggregation, as evidenced by increased particle size and turbidity and reduced solubility. Spectroscopic and molecular-force analyses revealed PHP-induced conformational rearrangements of MP, including decreased α-helix content, increased β-sheet structures, strengthened hydrophobic interactions and disulfide bonding, and adjustments in ionic and hydrogen bonding. Microstructural observations further showed that PHP effectively filled voids within the protein matrix and facilitated the formation of a more compact and continuous gel network. Overall, moderate PHP incorporation reinforced protein-polysaccharide interactions and improved the heat-induced gelation behavior of unwashed surimi. These findings highlight PHP as a functional bio-based additive with potential for engineering higher-quality, structurally stable surimi products.