Functionally Active Microbiome and Physicochemical Properties of Milk and Sugary Water Kefir from Brazil

Abstract

In Brazil, milk kefir, made of milk kefir grains, has identity features defined by Brazilian regulatory agencies but sugary water kefir, made of water kefir grains, has no definition of microbiological and physicochemical standards. We evaluated the microstructure of Brazilian milk and water kefir grains, the Transcriptionally Active Microbiome (TAM) of kefir beverages made of them, and the effect of fermentation and storage period (28 days at 10oC) over microbiological and physicochemical features of these beverages. Milk and water grains are very different between them and similar to other kefir grains worldwide, macroscopically and microscopically. The genus Leuconostoc, with the species L. mesenteroides, was most frequent in the microbiome of milk kefir while the Oenococcus genus was most frequently seen in sugary water kefir, with the species O. kitaharae. The genera Saccharomyces and Torulaspora, with the species S. cerevisiae and T. delbrueckii, were most recurrent in the microbiome of sugary water kefir, while Pichia and Yarrowia were more abundant in milk kefir, with the species P. fermentans and Y. lipolytica. Microbiological and physicochemical parameters of milk kefir were in concordance with features defined by Brazilian legislation. None of the parameters was altered by cold storage for 28 days. Our results reinforce some Brazilian identity requirements for milk kefir and allow us to suggest the inclusion of new ones that are not defined yet. Regarding sugary water kefir, some microbiological and physicochemical parameters are similar to milk kefir during the same storage period, although with a quite different functional microbiome.