Investigation of inhibition of lipid oxidation by L-carnosine using an oxidized-myoglobin-mediated washed fish muscle system

The objective of the present study was to understand mechanisms of inhibitory effect of l-carnosine on lipid oxidation using an oxidized myoglobin (metMb)-mediated washed cod muscle system. Experiments were conducted to compare l-carnosine with commercial antioxidants, tert-Butylhydroquinone (TBHQ) and α-tocopherol, and metal chelating reagent EDTA for inhibition of lipid oxidation, to compare l-carnosine with TBHQ for scavenging free radicals and to evaluate the effect of l-carnosine on structure of pro-oxidant metMb with spectral methods. Results showed that the inhibitory effect of l-carnosine on lipid oxidation was comparable with TBHQ and better than α-tocopherol. However, 1,1-diphenyl-2-picrylhydrazyl assay showed that TBHQ was much more effective in scavenging free radicals than l-carnosine. Comparing with 1.5% EDTA, 1.5% l-carnosine was much more effective against lipid oxidation. Incubation of l-carnosine with metMb resulted in spectral changes of metMb in wavelengths between 370 nm and 450 nm, Soret band shifted from 409 nm to 420 nm, and reduced molar ellepticity values. These results indicate that the high inhibitory effects of l-carnosine on meat lipid oxidation may result from not only its scavenging and chelating functions but also its effect on pro-oxidant metMb structure.