Antimicrobial, antioxidant, and sensorial impacts of oregano and rosemary essential oils over broccoli florets

Abstract

Combination of oregano and rosemary essential oils (EOs) was proposed to obtain a better antimicrobial and antioxidant effect on fresh-cut broccoli compared to the use of individual oils. In in vitro assays, EOs combinations (oregano + rosemary) were more effective to inhibit the growth of Escherichia coli O157:H7, Salmonella Choleraesuis, Listeria monocytogenes, and Staphylococcus aureus compared to individual EOs doses. Oregano EO showed a higher antioxidant power compared to rosemary tested by DPPH and TEAC methods. Moreover, oregano + rosemary EOs (concentrations of 0.24 + 0.91 mg/ml) added within pectin coatings reduced coliform counts by 1 log unit and yeasts and molds by 1.8 log of coated broccoli; meanwhile, individual application of EOs (oregano at 0.48 and rosemary at 1.82 mg/ml) was not as effective. It was demonstrated that a mixture of EOs offered antimicrobial protection to fresh-cut broccoli without negatively affecting its sensorial acceptability, even when no significant increment in its antioxidant capacity was observed. Practical applications Combination of essentials oils with different composition reduces the amount and costs of agents needed to inhibit bacterial growth and survival. The use of essential oils as oregano (Lippia graveolens) and rosemary (Rosmarinus officinalis) combined a diverse mixture of antibacterial compounds that could be a solution to avoid bacterial resistance developed for the treatment with single compounds. Additionally, the negative sensorial impact of higher single oils doses could be reduced when combined, creating a new range of flavors and odors.