Effects of Various Acids on Growth and Survival of Yersinia enterocolitica.

The relative effects of several different acids on survival of Yersinia enterocolitica in tryptic soy broth after 24 h of incubation were compared. The acids compared included 25, 50, 75, and 100 mW concentrations of hydrochloric (HCl), citric (CIT), acetic (ACE), lactic (LAC), propionic (PRO), or phosphoric (PHO) acid. The decrease in viable Yersinia cells was compared based on concentration of acid added, pH, and the calculated concentration of the undissociated portion of the monoprotic acids. In addition, data were subjected to analysis of variance procedures to determine significant differences among the antimicrobial activities of the various acids. Results indicated that the relative activity of the acids differed depending on how the data were compared. When based on equal molar concentration of acid added, the overall hierarchy of antimicrobial activity appeared to be CIT ⩾ HCl ⩾ LAC ⩾ PHO > PRO ⩾ ACE. The antimicrobial activity based on pH gave the apparent overall hierarchy PRO ⩾ LAC ⩾ ACE > CIT ⩾ PHO ⩾ HCl. The antimicrobial activity based on the concentration of the un-dissociated portion of monoprotic acids appeared to be HC1 > LAC > PRO ⩾ ACE. Although graphic representation of the data gave the appearance of differences in antimicrobial effects, statistical analysis revealed that often there was no significant difference (p⩽0.05) between acids. Differences which did appear were concentration-dependent. Statistical analysis also revealed that pH alone did not have a significant effect on survival.