An in‐situ method to track the quality change of frozen surimi as a whole: Multi‐molecular infrared spectroscopy in combination with LF‐NMR

The rapid overall characterization of quality changes in complex food systems is considered extremely challenging. Herein, a multi-molecular infrared spectroscopy (MM-IR) methodology in combination with low-field nuclear magnetic resonance and chemometrics, to in-situ reveal the quality changes of surimi (protein) products as a whole was developed. Surimi with cryoprotectant (SWC) and without cryoprotectant (SWO) were used as a typical demonstration. Specifically, secondary structures in proteins could transform into each other and the structural variation of SWC was smaller than that of SWO. Cryoprotectant could slow down the water conversion from non-moveable to free, thereby slow down the rate of protein degradation. principal component analysis results of massive samples verified the differences in quality between SWC and SWO at different storage stages. Therefore, the addition of cryoprotectant led to the frozen surimi having less protein secondary structure conversion and water migration. In sum, the developed MM-IR could be applicable for the quality tracking of frozen surimi. Practical applications Low-temperature storage is currently the most mainstream storage method for surimi, and the preservation time of surimi can be extended by adding cryoprotectants. In this study, the overall quality of frozen surimi could be characterized in situ and simultaneous multi-component analysis could be realized, and the changes in the secondary structure of surimi protein and the migration of water could be tracked in situ. The results of this work had the potential to track the quality changes of complex frozen aquatic products as a whole and predicted the frozen storage time.