Analysis of the release kinetics of taste substances in surimi gels with different cross-linking degrees

Flavor characteristics of surimi gels depend mainly on the cross-linking degrees induced by transglutaminase (TGase). This present study aims to explore the release kinetics of the taste substances in the surimi gels with different cross-linking degrees. The sodium chloride, sucrose, and monosodium glutamate were chosen as the typical taste substances in the surimi gels, representing the saltiness, sweetness, and umami taste, respectively. An electronic tongue analyzer was utilized to determine the taste profiles of surimi gels with the different TGase-induced cross-linking degrees. A sensory evaluation with/without the chewing process was selected to investigate the perception of saltiness, sweetness, and umami taste of surimi gels with the different cross-linking degrees. A simulated chewing test and the release kinetic analysis were also used to detect the release processes of sodium chloride, sucrose, and monosodium glutamate. Moreover, the release kinetic curves of the three taste substances were fitted with the pseudo-first-order and pseudo-second-order kinetic models for the release kinetic parameters. Additionally, the relationship was determined between the release parameters of taste substances in the surimi gels and the physicochemical properties of surimi gels with different cross-linking degrees. The results showed that there were significantly different taste characteristics of surimi gels, except for the surimi gels with high cross-linking degrees (61.8% and 71.2%). The saltiness in the surimi gels decreased with the cross-linking degrees increasing without the chewing process, while the umami taste increased significantly. Specifically, the chewing process increased the salty and umami perception, especially in the brittle gels with high cross-linking degrees (>42.2%). The simulated chewing test showed that the released concentrations of sodium chloride and sucrose in the surimi gels decreased first and then increased, as the cross-linking degrees increased, and reached the minimum when the cross-linking degree was 42.2% and 51.5%, respectively. Whereas, the released monosodium glutamate increased dramatically. The release curves of sodium chloride and sucrose were fitted with the pseudo-first-order kinetic model, indicating that the release process of two substances depended mainly on the boundary layer diffusion or the intra-particle diffusion. By contrast, the pseudo-second-order kinetic model was appropriate to fit the release process of monosodium glutamate, indicating that the chemical interactions were the rate-limiting step during the monosodium glutamate release process. The correlation analysis indicated that the release equilibrium capacity of sodium chloride was negatively correlated with the cross-linking degree and the brittleness of surimi gels, whereas that was positively correlated with the pore equivalent diameter and the ion bond contents. There was a negative correlation between the hydrogen bond contents and the released concentration during the simulated chewing process of sodium chloride. The release rate of sucrose showed a positive correlation with the pore equivalent diameter and the ion bond contents. More importantly, the released sucrose was positively correlated with the hydrophobic interactions during the simulated chewing process. All release parameters of monosodium glutamate whether chewing or not presented a positive relationship between the cross-linking degrees, the hardness, and the brittleness of surimi gels, indicating a negative correlation with the water holding capacity and the ion bond contents. In conclusion, the perception of tastes in the surimi gels with the different cross-linking degrees was influenced by the release behaviors of taste substances, the texture of gels during the chewing process, and the interactions between the taste substances and the gels. Especially, the chewing process can be expected to significantly enhance the release and the perception of taste substances in the surimi gels with high cross-linking degrees. This finding can provide a strong reference to control the tastes in the surimi-based products using cross-linking degrees.