The effects of fermentation with water kefir grains on two varieties of tigernut (Cyperus esculentus L.) milk

Abstract

This study investigated the effect on the brown and yellow varieties of tigernut milk after fermentation with water kefir grain, and then determined the properties and bioactive components of the resulting tigernut kefirs. The yellow variety of tigernut milk had higher glucose, fructose and sucrose concentrations. The lactococci and lactobacilli counts for the tigernut kefirs reached from 8.71 to 8.78 log CFU/ml and from 6.94 to 8.14 log CFU/ml, respectively. The presence of yeast in tigernut kefir is related to water kefir grain microbiota. Tigernut kefirs contained from 2.44 to 2.96 g/L of lactic acid. The stepwise discriminant analysis demonstrated that succinic acid, folate, vitamin E, and iron contents were found to be discriminating attributes of the tigernut milk varieties. In contrast, benzoic acid, quercetin and vitamin K were discriminating attributes for tigernut kefirs. The total phenolic content of the samples varied from 77.82 to 101.77 mg of gallic acid equivalents (GAE) L−1; the brown variety of tigernut kefir had a lower total phenolic content than the yellow variety. An increase in the total antioxidant capacity was noticed after kefir fermentation. The extensive findings of this study demonstrated that tigernut milk from both varieties provide an excellent environment for the growth of water kefir microbiota.