Inhibition of Streptococcus lactis and Salmonella typhimurium by Mixtures of Some Volatile and Non-Volatile Compounds Associated with Milk1

Abstract

APT broth inoculated with Streptococcus lactis or nutrient broth inoculated with Salmonella typhimurium was dispensed into epoxy-lined aerosol cans. Mixtures consisting of blends of fatty acids (10, 100, and 1000 ppm) containing formic, butyric, hexanoic, octanoic, and decanoic acid; amines (5 ppm) containing propyl- and hexylamine; and aldehydes and ketones (10 ppm) containing formaldehyde, acetaldehyde, acetone, 2-butanone, diacetyl, and pentanone were added to cans and they were sealed. Various combinations of fatty acids, amines, and aldehydes and ketones also were tested separately. Bacteria were enumerated at intervals during incubation at 30 or 37 C. Mixtures of fatty acids at a concentration of 1000 ppm were most detrimental to both organisms. A marked reduction in growth of S. lactis also occurred when 100 and 10 ppm of mixed fatty acids were tested. Growth of S. typhimurium was generally unaffected by 10 ppm of mixed fatty acids. Mixtures of amines and of aldehydes and ketones were more inhibitory to S. typhimurium than to S. lactis. Mixtures of all compounds (fatty acids, amines, aldehydes, and ketones) were significantly inhibitory to both organisms.