Excellent cultured milk questions!

Thanks everyone that has been checking my blog and for comments and questions you've left. Sarah- you posed some excellent questions that I want to answer in a post because I'm sure many people have wondered the same thing.

Q- When you make the cultured buttermilk yourself, how long does it last in the fridge?
A- I actually don't know how long it CAN last, because I've never let it just sit till it goes bad, but that would be an interesting experiment! My experience is that homemade buttermilk in a glass jar that I am using every few days will last about a month or so. In the beginning when I was just figuring this stuff out, I used to have problems with the remains that clung to the jar going moldy after awhile. I learned that if I poured the buttermilk into smaller jars after I'd used about 1/2 of the jar kept it fresher longer- it's the oxygen exposure that makes it go bad faster. Now I make a batch nearly every day so my buttermilk jar never has a chance to even start smelling "off". Just be sure to check to see if it the top part of the jar that has gone bad or if it really is the buttermilk itself before chucking the whole thing.

Another thing about buttermilk- sometimes buttermilk can go stringy, and this can be kind of gross. It still works, but it can make one wonder if it's good or not, and it's kind of a pain to work with. I have found that usually, if I just start a new batch-even using the stringy batch as my start if I have no other start- and let it sit longer (maybe a day and a half) so it gets real thick, then the you won't have the same problem the next time. I have used one start to make months and months of buttermilk, and sometimes wonder if it's still doing its job, but as long as it still continues to thicken the milk and it doesn't smell bad, it is still working. I am constantly amazed at how long one can go without starting over with a fresh start. I think the only way I've actually seen a start get "killed" is if it is heated above 110 or 120 degrees, then it will no longer culture milk.

Q- And I've been experimenting with kefir--how do I know if it is "working"? How do I know if the grains have gone bad?
A- A kefir start is working if it thickens the milk that it is put in. It will smell pleasantly sour when it is done, and you can make it less thick or more thick, depending on how long you culture it. You will know if your grains are not working because they will not thicken your milk. Usually it's not a case of them going bad, but more likely that they haven't cultured long enough. Always let them sit a little longer before deciding that they don't work (anywhere between 18 and 48 hours is normal).

Q- How do I know if I'm drinking correctly fermented milk, or rotten milk that sat out on the cupboard all day? :)
A- Correctly fermented milk is thicker and smells pleasantly sour. You couldn't make yourself drink rotten milk if you tried because the smell would be so bad. The wonderful thing about raw milk is that if it is good, you know by the smell. If it is bad, you know by the smell! If it smells sweet (fresh milk) or sour (cultured milk), it is fine. If it smells putrid, throw it out.