When you make your own yogurt — which I highly recommend — you need some sort of starter. If you make yogurt regularly, you simply set aside a little bit of each batch — maybe three or four tablespoonfuls — to serve as the starter for the next batch. That starter can be frozen if you don’t make yogurt quite as often, and that’s what I usually do. You don’t want to leave it in the freezer forever, though; if it starts to get freezer burn, it may not be as effective.
But you don’t always have your own yogurt to use as a starter. Maybe you’re making yogurt for the very first time, or for the first time in many months or years. Maybe you forgot to set aside starter the last time. Maybe your last batch of yogurt didn’t turn out, which happens occasionally.
In cases like this, you can either use a little bit of store-bought yogurt (the freshest you can find, and make sure it’s labeled as having “live and active” yogurt cultures), or a little packet of freeze-dried yogurt starter.
I am partial to the freeze-dried starter. If I have a few packets of starter stashed away, they’re always on hand when I need them. And you can find a variety of freeze-dried starters. Some promise specific probiotic health benefits. Some claim to be heirloom starters, handed down for generations.
A couple of weeks back, I went to make yogurt and decided that my starter looked a little freezer-burnt. It’s been a busy summer, and I had not made yogurt in a while. I had some freeze-dried starter; it’s a brand I’ve used before, but this was the first packet from an unopened bag of five packets.
The yogurt didn’t turn out. As I said, this happens occasionally. It was only slightly thickened and had a weird bitter taste. There were any number of possible explanations. I might have failed to let the milk cool down well enough after scalding it. If you add the starter to milk that is too hot, it can kill the starter. There could have been some chemical or mold spore in the air (or I could have failed to clean my utensils well enough beforehand).
So I tried again a few days ago — and got exactly the same result. I’m not 100 percent sure what the cause is, but for the moment I’m assuming I somehow got a bad batch of freeze-dried starter. I ordered a different brand of starter from Amazon, and it arrived today. I have just finished scalding the milk and adding the starter; I’ll know late tonight whether it worked. If the yogurt doesn’t set up, it will be back to the drawing board.