Inhibition of enterobacteria andListeriagrowth by lactic, acetic and formic acids

摘要

Minimum inhibitory concentrations (MIC) of undissociated lactic, acetic and formic acids were evaluated for 23 strains of enterobacteria and two ofListeria monocytogenes.The evaluation was performed aerobically and anaerobically in a liquid test system at pH intervals of between 4.2 and 5.4. Growth of the enterobacteria was inhibited at 2–11 mmol 1−1, 0.5–14 mmol 1−1and 0.1–1.5 mmol 1−1of undissociated lactic, acetic and formic acids, respectively. The MIC value was slightly lower with anaerobic conditions compared with aerobic conditions. The influence of protons on the inhibition was observed for acetic acid at the low pH values. Undissociated lactic acid was 2 to 5 times more efficient in inhibitingL. monocytogenesthan enterobacteria. Acetic acid had a similar inhibitory action onL. monocytogenescompared with enterobacteria. Inorganic acid (HCl) inhibited most enterobacteria at pH 4.0; some strains, however, were able to initiate growth to pH 3.8. The results indicate that the values of undissociated acid which occur in a silage of pH 4.1–4.5 are about 10–100 times higher than required in order to protect the forage from the growth of enterobacteria and L