Milk Kefir Basics
Milk kefir is the original and true fermented milk drink made with 'Kefir' grains (a yeast/bacterial fermentation starter) and this shared use of the name 'Kefir' is why Water Kefir is regularly confused with Milk Kefir. Water Kefir is wrongly referred to as 'Kefir' and it's proper name is generally 'Tibicos'. While what most people call Water Kefir ferments sugared water, true Kefir (Milk Kefir) is prepared by inoculating cow, goat, or sheep milk with kefir grains.
Simply put, Milk kefir grains ferment the sugars in animal milks (lactose) while Water Kefir grains ferment the plant sugars (sucrose) in a sugar water solution. One is simply plant based while the other is animal based and they cannot be combined or used in their opposite medium.
Traditional kefir was made in skin bags that were hung near a doorway; the bag would be knocked by anyone passing through the doorway to help keep the milk and kefir grains well mixed.
Kefir grains are a combination of lactic acid bacteria and yeasts in a matrix of proteins, lipids, and sugars, and this symbiotic matrix, (or SCOBY) forms "grains" that resemble cauliflower.
For this reason, a complex and highly variable community of lactic acid bacteria and yeasts can be found in these grains although some predominate; Lactobacillus species are always present. Even successive batches of kefir may differ due to factors such as the kefir grains rising out of the milk while fermenting, or curds forming around the grains, as well as variations in room temperature.The resulting ferment, once strained, is a runny, rather sour yoghurt like drink with high numbers of probiotic bacteria.