Highlights
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Kefirs were prepared with inoculation of natural Kefir grains into Saanen, Hair Goat and cow's milk.
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Goat kefir had higher content of useful microbiota; Lactobacillus acidophilus and Bifidobacterium spp.
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Kefir fermentation significantly affected antioxidant activity (ORAC and TEAC values).
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Hair goat kefir had highest bioactive substances such as gallic acid, catechin, epicatechin.
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Goat Kefir with superior microbial and antioxidant activity would be a functional beverage in diet.