INHIBITION OF BACTERIA BY SOME VOLATILE AND NON-VOLATILE COMPOUNDS ASSOCIATED WITH MILK

Abstract

Nutrient broth inoculated with Staphylococcus aureus was dispensed into aerosol cans with an epoxy lining. Twenty-five volatile or non-volatile compounds were individually added to these cans to yield final concentrations of 1, 10, 100, and 1000 ppm of each compound. The compounds used included fatty acids (formic, acetic, butyric, hexanoic, octanoic, and decanoic), aldehydes (formaldehyde, acetaldehyde, propionaldehyde, and glyoxal), ketones (acetone, 2-butanone, and diacetyl, amines (propyl- and hexylamine), alcohols (furfurol and methanol), sulfur compounds (methylsulfide, methylsulfone, methanethiol, and ethanethiol), acetonitrile, chloroform, ether, and ethylenedichloride. Bacteria were enumerated at intervals during incubation at 37 C.At 1000 ppm butyric acid was least inhibitory of the fatty acids, but at 10 ppm, butyric, octanoic, and decanoic acid were more effective against S. aureus than were the other fatty acids. Formaldehyde was most inhibitory of the aldehydes tested, whereas propionaldehyde was least effective. Diacetyl was most detrimental of the ketones tested. Chloroform at 1000 ppm inactivated S. aureus. Acetonitrile, ether, ethylenedichloride, and methylsulfone were significantly inhibitory to S. aureus only at higher concentrations. Lower concentrations of methylsulfide, methanethiol, and ethanethiol sometimes significantly enhanced growth of S. aureus. Amines were more inhibitory to S. aureus than were the alcohols.