Isolation and characterization of the microbial population of different South African kefir grains

International Journal of Dairy Technology - Tập 57 Số 1 - Trang 33-37 - 2004
R. Corli Witthuhn1, Tersia Schoeman1, T.J. Britz1
1Department of Food Science, Stellenbosch University, Private Bag XI, Matieland, 7602, South Africa

Tóm tắt

Kefir, a slightly acidic fermented milk, is produced by adding lactic acid bacteria and yeasts, in the form of grains, to milk. The bacteria and yeasts present in the kefir grains are known to vary widely. Selective growth media and morphological and biochemical characteristics were used for the isolation and identification of the microbes present in the grains from eight different sources in South Africa. The kefir grains were activated in milk for only 24 h to prevent any changes in the microbial population of the grains. The microbial numbers varied between 6.4 × 104and 8.5 × 108 cfu/g on the media selective for the bacterial species and between 1.5 × 105and 3.7 × 108 cfu/g on the media selective for the yeast species. The bacterial genera that were identified included Lactobacillus, Leuconostoc and Lactococcus and the yeast genera included Zygosaccharomyces, Candida and Saccharomyces. The distribution frequencies of the microbes in the different grains were determined and most of the grains were dominated by two microbial species. No pediococci, acetic acid bacteria or propionibacteria were detected.

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