Enhanced sodium release and saltiness perception of surimi gels by microwave combined with water bath heating

The study aims to use thermal processing to enhance sodium release from surimi matrix during oral processing and therefore improve the saltiness perception. Surimi gels were prepared by one- and two-stage heating, containing water bath heating (WB90), microwave heating (MW10), two-stage water bath heating (WB40+WB90), and water bath combined with microwave heating (WB40+MW10). The physicochemical properties including gel strength, protein degradation, and microstructure of surimi gels were compared. The water and sodium mobility of surimi gels were characterized by 1H low field NMR and 23Na NMR. Sodium release from matrix during oral processing and sensory evaluation of saltiness difference were employed to verify the enhancement effect of saltiness perception caused by thermal processing. WB40+MW10 improved surimi gel strength by reducing the degradation of myosin heavy chain. Microstructure observations showed that WB40+WB90 gels had a relatively rough and loose microstructure with curved small gaps, whereas WB40+MW10 gels exhibited a denser microstructure. The water and sodium mobility of WB40+MW10 gels (T21 88.08 ms, D 6.68 × 10−10 m2/s) were significantly higher than those of WB40+WB90 gels (T21 83.10 ms, D 6.35 × 10−10 m2/s). WB40+MW10 gels eliminated the tortuosity effect of water and sodium diffusion, resulting in 1.12 times higher sodium release than WB40+WB90 gels. The triangle sensory evaluation also showed that WB40+MW10 gels were perceived as saltier than WB40+WB90 gels, achieving a 15% salt reduction effect. This study provides a promising heating method to improve the saltiness perception of fish products by enhancing sodium release during oral processing.