Abstract:
To investigate the effects of precision feedback microwave heating (PFMH) on the gel properties of
Nemipterus virgatus surimi, this study used
Nemipterus virgatus surimi as the research subject. The study analyzed the changes in gel strength, water-holding capacity (
WHC), textural properties, whiteness, moisture distribution, microstructure, protein distribution, and protein secondary structure of the surimi gels under different temperatures and heating durations conditions of PFMH, with two-stage water bath heating as the control. The results indicated that the gel strength of surimi gels heated by PFMH at 85 ℃ for 1 min increased by 58.21% compared to the control group, reaching
6855.66 g·mm. However, the gel strength of surimi gels treated at 80 and 90 ℃ was lower than that of the control group. Compared with the control group, the hardness and adhesiveness of surimi gels treated by PFMH increased by 30.17%~37.06% and 19.82%~25.37%, respectively, indicating that the texture properties of surimi gels were improved. Although the whiteness of the surimi gels treated with PFMH decreased by 2.11% to 6.44%, the color difference was not discernible to the naked eye. The water-holding capacity of surimi gels treated with PFMH increased by 1.25% to 9.18%, suggesting that PFMH can strengthen the binding between proteins and water, effectively reducing water mobility. Results from low-field nuclear magnetic resonance and imaging revealed that the relaxation times of surimi gels treated with PFMH shifted significantly to the left compared to the control group. The imaging colors of samples heated at 85 ℃ for 1 min and at 80 ℃ for 3 min appeared the reddest, indicating the highest proportion of immobile water. This suggests that PFMH can lock moisture within the surimi gels, promoting a uniform distribution of water. Furthermore, microstructural analysis showed that, compared to the control group, the surface of surimi gels treated with PFMH were smoother, exhibiting a denser network structure and more orderly pores. The surimi gel treated under PFMH at 85 ℃ for 1 min exhibited the smallest pores with uniform distribution. The
Df value of the surimi gel heated at 85 ℃ for 1 min was the highest at
1.9695, demonstrating a more compact and uniform microstructure which can effectively retains moisture. Confocal laser scanning microscopy results showed that the protein particles in the surimi gel of the control group were more dispersed, but the protein distribution in the surimi gel treated at 85 ℃ for 1 min was more uniform and the particle size was consistent. Regarding the protein secondary structure, the results showed that PFMH treatment at 85 ℃ for 1 min reduced the
α-helix content to 38.22% while increasing the
β-sheet content to 32.49%. This indicated that under these conditions, the protein secondary structure became more ordered, effectively facilitating the transition of protein conformations toward a more structured state. This study employed PFMH to heat surimi with the aim of improving its gel quality, reducing wastewater discharge, and achieving green and low-carbon production. The findings provide theoretical references and technical support for the deep processing of
Nemipterus virgatus.