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

Authors: XIAO, SHULAN - Nanjing Agricultural University; Zhuang, Hong; ZHOU, GUANGHONG - Nanjing Agricultural University; ZHANG, JIANHAO - Nanjing Agricultural University

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2018
Publication Date: 8/23/2018
Citation: Xiao, S., Zhuang, H., Zhou, G., Zhang, J. 2018. Investigation of inhibition of lipid oxidation by L-carnosine using an oxidized-myoglobin-mediated washed fish muscle system. LWT - Food Science and Technology. 97:703-710.

Interpretive Summary: Lipid oxidation in meat and meat products has been one of main quality concerns to meat industry It negatively affects meat quality, such as color, texture, flavor, and nutrition. Food industry and researchers have been trying to find effective strategies to inhibit lipid oxidation in meat with no harmful side effect during food processing and storage. Synthetic antioxidants, such as Butyl hydroxyanisole (BHA) and tert-Butylhydroquinone (TBHQ), are commonly used in food to control lipid oxidation. However, their usage has become health concerns due to their toxic properties. Therefore, food scientists are looking for antioxidants present in nature as alternatives. L-carnosine is a natural antioxidant, which exists with high content in skeletal muscle and has shown antioxidative activities in meat products. L-carnosine can effectively inhibit lipid oxidation induced by not only metal catalysts, iron and copper, but also pro-oxidant proteins, such as heme-proteins and lipoxygenase. In this study, we investigated the possible mechanisms of antioxidant L-carnosine against lipid oxidation in meat by using a fish meat model system. Our study shows that L-carnosine can inhibit lipid oxidation mediated by heme proteins as effectively as TBHQ. As a natural antioxidant, L-carnosine showed much stronger antioxidant capability than a-tocopherol. By comparison with metal chelating reagent EDTA and free radical scavenging chemical TBHQ, the inhibition of lipid oxidation in meat by L-carnosine may not be due to only the chelation of prooxidant metals and free radical scavenging. Indirect measurements of structure of metMb with spectroscopic methods indicate that L-carnosine also induce structural change of pro-oxidant heme proteins, which may also play a role in antioxidant effects of L-carnosine.

Technical Abstract: 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 a-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 a-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.