Abstract:

Common processed fish products in the market were investigated in this study to determine and correlate the contents
of carbonyl group, thiol group and disulfide bond, as well as protein hydrophobicity. The results showed that different processed
fish products exhibited significant differences in the contents of carbonyl group, thiol group and disulfide bond, as well as protein
hydrophobicity (P < 0.05). The carbonyl content of cold fresh products was low (0–1 nmol/mg), while the carbonyl content of
salted products was the highest (6–10 nmol/mg). The thiol group content of frozen fresh products was higher (70–100 nmol/mg),
and the disulfide bond content was the lowest (0.1–0.2 nmol/mg). In other processed fish products, the thiol group content was
30–70 nmol/mg, and the disulfide bond content was 1–5 nmol/mg. Correlation analysis revealed that there was a significant correlation
between carbonyl content and protein hydrophobicity (r = 0.84, P < 0.01). A significant relationship existed between thiol group
content and disulfide bond content (r = −0.59, P < 0.05). Our experimental results showed that the degree of protein oxidation was
higher in roasted and salted products than dried products; the lowest degree of protein oxidation was found in frozen fresh products.

Key words: protein oxidation, fish products, carbonyl group, thiol group, protein hydrophobicity