Abstract: In this paper, large yellow croaker was subjected to ultra-high pressure treatment at pressures of 150, 200, 250, 300, 350, 400, 450 and 500 MPa for different durations of 5, 10, 15, 20, 25 and 30 min for modification of myofibrillar proteins. The endogenous fluorescence intensity of myofibrillar proteins was determined by fluorescence spectrophotometry, the myofibrillar protein functional structure was determined by Fourier transform infrared spectroscopy, and the secondary structure was determined by circular dichroism spectroscopy. Raman spectroscopy was employed to determine the information about chemical groups in the proteins, and the microstructure changes were observed by scanning electron microscopy. The results showed that the fluorescence intensity and maximum emission wavelength of myofibrillar proteins were influenced by pressure and holding time, and the maximum fluorescence emission intensity increased with the increase in the variables. Ultra-high pressure treatment affected the tertiary structure of myofibrillar proteins and enhanced the polarity of the surrounding environment of amino acid residues. Ultra-high pressure also affected the secondary structure; the content of α-helix structure gradually decreased with the increase in pressure and holding time. Moreover, ultra-high pressure affected protein conformational changes and caused protein denaturation; the degree of denaturation, directly affecting the microstructure of myofibrillar proteins, was positively correlated with pressure and holding time. Conclusively, the secondary and tertiary structure of myofibrillar proteins from cultured large yellow croaker was changed after ultra-high pressure treatment, causing protein denaturation and accordingly quality changes of fish meat.

Key words: high hydrostatic pressure, cultured large yellow croaker, myofibrillar protein, structure