Abstract: The aim of this study was to study the effects of plasma-activated water (PAW) brine on the oxidation and structure of pork myofibrillar protein. PAW was prepared by using plasma jet to treat distilled water for 0, 40, 60, and 80 s under the conditions of output voltage 20 kV, and current 0.025 mA, and then PAW and distilled water (as a control) were separately added with 8% NaCl, 3% sugar and 0.5% sodium pyrophosphate. Meat samples were marinated in the control and PAW brines with a 2:1 (m/m) ratio of meat to brine at 10 ℃ for 12 h. Afterwards, the oxidation, surface hydrophobicity and secondary structure of pork myofibrillar proteins were studied by analysis of total sulfhydryl and carbonyl contents, free amino acid contents, Fourier transform infrared (FTIR) spectra and protein surface hydrophobicity index (S0-ANS). The results showed that PAW curing could significantly increase the extent of protein oxidation (P < 0.05); the carbonyl content in the 40, 60 and 80 s treatments increased by 0.67, 1.42 and 1.57 nmol/g, respectively, compared with the control, while the total sulfhydryl content decreased by 14.51%, 19.35% and 30.65%, respectively. PAW loosened the compact protein structure; the proportion of α-helix in 40, 60 and 80 s treatments decreased by 10.73%, 20.71% and 33.32%, respectively, the proportion of β-sheet increased by 7.78%, 11.87% and 16.41%, respectively, the proportion of random coil increased 6.50%, 17.38% and 26.23%, while the proportion of β-turn did not change significantly in comparison with the control group. The contents of glutamic acid, phenylalanine, alanine, glycine, tyrosine and arginine significantly increased in the 60 and 80 s treatments. S0-ANS significantly decreased in the 40 s treatment but increased by 12.72% and 36.36% in the 60 and 80 s treatments, respectively. In conclusion, PAW brine could induce the oxidation of myofibrillar proteins and alter the secondary structure.

Key words: plasma-activated water; myofibrillar protein; plasma jet; structure; protein oxidation