I recently received from a friend a batch of live kefir grains, by mail. The grains were packaged for a few days in a little jar filled with water. As soon as I received them, I put them in some half-skimmed milk (probably too little for the amount of grains I received), and for the following week I could not take care of them, so I left them in the fridge with the milk.
A few days ago I had a look at them, to see if anything happened, and to try reviving them. However, the milk seemingly did not change consistency. I strained the grains out, noticing a very strong yeasty-alcoholic smell. I dropped that batch of milk, but I retried (unfortunately again with some more half-skimmed milk) leaving them at room temperature for the night.
The following batch still did not thicken at all, but the smell was really interesting: exactly like beer. Out of curiosity I tasted a few drops of it, and it also tastes good, just like regular beer.
I wasn't confident enough to drink more than that, but my question is: can kefir grains change milk into some milk-based, beer-like beverage? If so, is it safe to drink? And what caused this weird behavior?