We heat it for longer, so it's more like a Greek yogurt than the drink. The problem is, it only lasts for four or five days, and if you don't eat the full litre in that time, the 'seed' from which we grow the next bit starts to turn off, and I use a sniff test to know whether it's any good. We can't always get a vegan kefir as a new seed, but we try to make our own kefir last, and keep it going all year, so the problem doesn't arise very often. It's just like making yogurt basically, but kefir has other alleged health benefits from a broader range of healthy microbes.