Xanthan gum-based film-forming suspension containing essential oils: Production and in vitro antimicrobial activity evaluation against mastitis-causing microorganisms

In this work, xanthan gum-based films incorporating clove, cinnamon, and oregano essential oils (EO) were proposed as potential natural antimicrobial films, aiming "post-dipping" mastitis prevention and, consequently, to reduce the foodborne pathogens in milk. The antimicrobial activity of the film-forming suspensions was tested against on standard strains of Staphylococcus aureus, Escherichia coli and Candida albicans by agar well diffusion technique and by a quantitative assay applying the formulations on the surface of the agar. Emulsions containing 0.1, 0.3, 0.5, 1.0, 2.0 and 3.0 wt% of each EO were prepared by two different methodologies, the simple dispersion (FSSD) and nanoemulsification (FSN) ultrasound, then added to a primary xanthan gum-based filmforming formulation. The diffusion tests in agar showed that the microorganisms were more susceptible to FSSD than to FSN formulations, mainly for oregano and cinnamon oil at 2.0 and 3.0 wt%. The inhibition zones for the FSSD samples containing oregano or cinnamon oils had similar antimicrobial activity to the positive control. The quantitative tests showed that both FSN and FSSD were very effective at oil concentrations, above 1.0 wt%, inhibiting the growth of all microorganisms. The results showed that the present antimicrobial xanthan gumbased film-forming suspensions have potential to control the investigated pathogens and prevent bovine mastitis.