Combination of Cymbopogon citratus and Allium cepa essential oils increased antibacterial activity in leafy vegetables.

BACKGROUND: Cymbopogon citratus and Allium cepa essential oils (EOs) are rich in terpenes and sulfur compounds respectively, both with antibacterial activity and different cell targets, supporting the idea that their combination can increase their efficacy.

RESULTS: Major constituents of C. citratus were geranial and neral, while A. cepa presented dipropyl disulfide and dipropyl trisulfide. Cymbopogon citratus and A. cepa EOs inhibited the in vitro growth of Escherichia coli O157:H7 (minimal inhibitory concentrations of 2.21 and 5.13 g L(-1) respectively), Salmonella Choleraesuis (3.04 and 1.28 g L(-1) ), Listeria monocytogenes (1.33 and 2.56 g L(-1) ) and Staphylococcus aureus (0.44 and 5.26 g L(-1) ). Application of the EO combination to spinach caused a greater reduction in E. coli (2.34 log colony-forming units (CFU) g(-1) ), S. Choleraesuis (2.94 log CFU g(-1) ), L. monocytogenes (2.06 log CFU g(-1) ) and S. aureus (1.37 log CFU g(-1) ) compared with higher doses of individual EOs; a similar effect was observed for romaine lettuce. Individual and combined EOs caused a reduction in flavor acceptability level; however, no significant differences were found among odor acceptability of control vegetables and those treated with the EO combination and C. citratus EO.

CONCLUSION: Leafy vegetables treated with the EO combination showed higher antibacterial protection and odor acceptability compared with individual EO treatments. © 2016 Society of Chemical Industry.