Effect of smoke processing on the proteins and volatile compounds and their interactions in skipjack tuna

Abstract

Characterizing the correlation between protein structure and flavor features is crucial for maintaining the quality of smoked skipjack tuna meat during freezing, heating, smoking, steaming, and slicing. This study provides a comprehensive analysis of protein structure, including sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR). The volatile flavor compounds (VFCs) were tentatively identified using Gas chromatography-mass spectrometry (GC–MS). Partial Least Squares Regression (PLSR) analysis was employed to demonstrate the correlation between VFCs and proteins. The results of free-sulfhydryl content and solubility analyses revealed that proteins underwent aggregation during the process due to the formation of disulfide bonds and cross-linking with smoke compounds. The results of SDS-PAGE further indicated that the proteins with molecular weights ranging from 45 to 140 kDa interacted with smoke compounds during the smoking stage. The FTIR results revealed that hydrogen bonding and hydrophobic interactions were the dominant factors in the processing. Except for the smoking stage, the thermal stability of skipjack tuna meat diminished in all processing stages. A total of 121 VFCs were identified, with phenols and pyrazines notably appearing during the smoking stage due to wood smoke decomposition. The PLSR analysis suggested that the free sulfhydryl groups are primarily responsible for the alterations in VFCs during the heating process, while changes in VFCs during smoking are mainly influenced by hydrogen bonding. The findings offer a comprehensive perspective on the alterations in protein structure that influence the formation of VFCs during processing, thereby expanding the applications of smoked skipjack tuna.