The kefir grains separated from fermented milk and washed with water were not
contaminated when inoculation of milk with E. coli before fermentation did not
exceed 6.1×102 cfu.mL−1. In the postharvest broth, contamination was found at
inoculation rate, and in spite of demonstrated inhibitory activities against E. coli, it
cannot be used as starter culture for kefir production. In contaminated milks
incubated at the same conditions without kefir grains, the population of E. coli
increased by 3 log in average. Kefir grains separated from contaminated milk
retained their replication ability in milk and allowed obtaining uncontaminated
postharvest broth with similar characteristic to uncontaminated grains in respect of
milk acidification profile and ratio of total LAB count to citrate-fermenting and
vancomycin-tolerant LAB, and yeasts. The study has demonstrated that kefir grains,
after separation from contaminated fermented milk, can be considered for re-use in a
dairy plant for starter culture production.