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

Abstract

Nutrient broth inoculated with Escherichia coli was dispensed into epoxy-lined aerosol cans. Twenty-five milk-associated volatile or non-volatile compounds were then added individually to cans to yield final concentrations of 1, 10, 100, and 1000 ppm of the compound. Compounds used included fatty acids (formic, acetic, butyric, hexanoic, octanoic, and decanoic acid), 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), acetronitrile, chloroform, ether, and ethylenedichloride. Bacteria were enumerated at intervals during incubation at 37 C. Fatty acids at a concentration of 10 ppm and sometimes at 1 ppm were inhibitory to E. coli; formic acid was most inhibitory. Formaldehyde was more detrimental to E. coli than glyoxal, acetaldehyde, or propionaldehyde. The lower concentrations of aldehydes (10 and 1 ppm) were only marginally inhibitory. Diacetyl was most inhibitory of the ketones tested. Acetonitrile (10 ppm), chloroform (10 ppm), ether (100 ppm), ethylenedichloride (10 ppm), and methylsulfone (10 ppm) caused statistically significant inhibition of E. coli. Ethanethiol was more detrimental than methylsulfide or methanethiol. Generally, amines (1 ppm) were more inhibitory than alcohols.