Antioxidant and antimicrobial activities of leafy green vegetable extracts and their applications to meat product preservation

Leafy green vegetables (LGV) are rich in phenolic compounds that have a wide range of biological functions, including antioxidant and antimicrobial activities. Our first goal was to evaluate the antioxidant and antimicrobial activities of 70% ethanolic extracts of ten LGV commonly consumed in East Asia. To determine antioxidant activity, we measured total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2-azinobis-3 ethyl benxothiazoline-6-sulphonic acid (ABTS) cation decolorization activity, and reducing power. For the analysis of antimicrobial activity, the inhibitory effects of the extracts against Escherichia coli, Salmonella enterica, Shigella flexneri, Listeria monocytogenes, Staphylococcus aureus, and Bacillus subtilis were evaluated using agar well diffusion and broth-microdilution tests. Among all LGV, extracts of chamnamul (Pimpinella brachycarpa) and fatsia (Aralia elata) exhibited outstanding antioxidant and antimicrobial properties, and we thus investigated the influences of these extracts on lipid oxidation and microbial criteria in raw beef patties. The extracts and butylated hydroxytoluene (BHT, a positive control) were individually added to patties at both 0.1% and 0.5% (w/w) concentrations and the patties were stored at 4 °C for 12 days. The color parameters and thiobarbituric acid reactive substances (TBARS) values were monitored periodically, and a microbial analysis was performed. The addition of extracts and BHT resulted in concentration-dependent decreases in TBARS values and in the number of microorganisms in the beef patties and also improved meat color stability. The fatsia extract had more effective antioxidant and antimicrobial activities than the chamnamul. We conclude that extracts of LGV, especially fatsia, have potential as natural preservatives for meat products.