Abstract: In order to investigate the effects of ultra-high pressure (UHP) and heat treatment on the oxidation, characteristics and structure of myofibrillar protein in sauced sheep tripe, samples were subjected to ultra-high pressure treatment (UHPT) with 400 MPa for 15 min or heat treatment (HT) in water bath at 85 ℃ for 40 min, packaged in vacuum and stored at 4 ℃. An untreated sample was used as a control. The effect of the treatments on myofibrillar protein oxidation and properties was evaluated through measuring carbonyl content, total sulfhydryl content, protein composition, solubility and turbidity. The protein structure was analyzed by ultraviolet absorption spectroscopy, endogenous fluorescence spectroscopy and Raman spectroscopy. The results showed that the carbonyl content of both the treated samples increased faster in the early storage period than did the control, and in general a higher level was observed in the UHPT group in comparison with the HT group. During storage, total sulfhydryl content decreased first and then increased for all groups, and dropped faster in the early storage period in both treatment groups compared with the control group. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that secondary sterilization mainly affected actin and tropomyosin. Both treatments significantly affected the turbidity of myofibrillar protein solution (P < 0.05) with the effect of UHP being weaker. Spectral analysis showed that both treatments transferred tryptophan residues to a non-polar environment, resulting in a decrease in the relative content of α-helix and an increase in the relative content of random coil and folding ratio. The treated protein was transformed from an ordered to a disordered state with the prolongation of storage time. Correlation analysis showed that storage time was significantly correlated with total sulfhydryl content, solubility, and the relative contents of α-helix, and protein oxidation was correlated with protein properties and structure. UHP was more advantageous in preserving the quality of sauced sheep tripe during storage.

Key words: ultra-high pressure; heat treatment; protein oxidation; sauced sheep tripe; myofibrillar protein