Synergistic Antimicrobial Effect of Acetic Acid, Sodium Chloride and Essential Oil Components

Abstract

Acetic acid, NaCl and essential oil components were examined for their synergistic antimicrobial effect, using air-borne microorganisms and purely cultured fungi. Antimicrobial assays were carried out at 27°C, using 2% glucose Sabouraud agar. In order to completely suppress the growth of all the contaminating air microorganisms over a period of one month, more than 0.2% acetic acid or more than 25% NaCl was required in the medium. Any one of the essential oil components examined, at a concentration of as high as 1 mM or more, permitted considerable growth of various air microorganisms within several days after contamination. However, in combination with both 0.1% acetic acid and 3% NaCl, perillaldehyde, citral (α,β-unsaturated aliphatic aldehydes), citronellol, geraniol, perillalcohol (primary alcohols) or cuminaldehyde, at a concentration of 0.5 mM, completely suppressed the growth of all the contaminating air microorganisms over a period of one month. Cinnamaldehyde was approximately twice as potent as these compounds in this respect, L-Menthol (secondary alcohol) and D-carvone (α,β-unsaturated ketone), at a concentration of 1 mM but not 0.5 mM, completely suppressed such microbial growth under the same exprimental conditions. Citronellal (α,β-saturated aldehyde) and linalool (tertiary alcohol) were somewhat less effective than L-menthol and D-carvone. Hydrocarbons examined (D-limonene, α-pinene, β-pinene, camphene, β-myrcene, β-caryophyllene and p-cymene), even at 2 mM, were only moderately effective in this respect. Similar synergistic antimicrobial effects of these substances were observed when using purely cultured fungi. These results strongly suggest that acetic acid, NaCl and certain essential oils (or their components), when combined together, are applicable at relatively lower concentrations for effective preservation of certain foods without applying synthetic preservatives. © 1982, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.