Influence of phenolic compounds on physicochemical and functional properties of protein isolate from Cinnamomum camphora seed kernel

Cinnamomum camphora seeds are abundant in China. For high value utilization of Cinnamomum camphora seed kernel (CCSK) protein, the effects of phenolic compounds on physicochemical and functional properties of protein isolate (PI) from CCSK were investigated in this study. A total of 12 phenolic compounds in CCSK have, for the first time, been tentatively identified by HPLC-ESI-QTOF-MS2. PI had a higher level of protein content compared to that of protein-phenolic complex (PPC). The formation of PPC resulted in a reduction of free sulfhydryl groups content and surface hydrophobicity as well as an increase of particle size and zeta potential. Fourier-transform infrared spectroscopy showed that the contents of secondary structure of PI and PPC were not obviously different. However, a remarkable increase in beta-sheet and a decrease in random coil of PPC compared to PI were found by circular dichmism. Differential scanning calorimetry analysis revealed that PPC was thermally more stable than that of PI. PI and PPC exhibited superior essential amino acid composition and similar protein subunits. Furthermore, PPC exhibited higher solubility, better foaming and emulsifying properties than those of PI. These results suggested that the protein products from CCSK may be used as natural functional materials in the food industry.