Inhibitory power of kefir: the role of organic acids

GARROTE G L; ABRAHAM A; DE ANTONI G

JOURNAL OF FOOD PROTECTION

Año: 2000 vol. 63 p. 364 - 369

0362-028X

Milk and MRS broth fermented with kefir grains from different households were examined for inhibitory activity towards gram-negative and gram-positive strains. Fermented milk obtained with 10 g/100ml inoculum (final pH 3.32 - 4.25) as well as MRS broth fermented with 1 and 10 g/100ml inocula (final pH 4.18 - 5.25) had inhibitory power demonstrated by spot test and agar well diffusion assay. This inhibitory effect could be assigned to the undissociated form of lactic and acetic acid produced during the fermentation process. Kefir supernatants inhibited the growth of Escherichia coli 3 in nutrient broth at 37°C for 24 hours. However, supernatants of yogur or milk artificially acidified with lactic and acetic acids  allowed the growth of Escherichia coli 3 in the same conditions. A bacteriostatic effect of milk fermented with kefir grains over Escherichia coli 3 was also demonstrated