Different Brands of Milk May Affect Yogurt-Making

I had a yogurt-making experience that I wanted to share, in the event that this might happen to someone else.

I've been making yogurt since 2012 and up until my batch at the end of February, I'd never had the yogurt not set-up. With that last batch, the yogurt only partially set. I'm careful about using the correct temperatures during each step (and I even calibrated my thermometer to be certain). I couldn't figure out what went wrong. I use starter from previous batches that I freeze in small amounts shortly after the yogurt is completed. I was down to just one container of starter in my freezer after this failed batch. On a hunch, I decided to try a different brand of milk for the next batch of yogurt, using this last container of starter.

Success! This batch of yogurt set-up beautifully. I don't really know what was different about the milk used in the failed batch. I had noticed that my yogurt this winter had been missing it's usual tang. So something was definitely different about that milk. With this recent batch, the yogurt is not only thick, but that tang is back.

Here's my message for anyone who makes their own yogurt and has a failed batch: After you've considered everything about your process, such as the temperatures for each heating and cooling step, the constancy of temperature maintained in your incubator while the yogurt was setting, the viability of your starter, and the ratio of starter to milk, try a different brand of milk. One brand may be pasteurized and processed in a slightly different way from another. This may not change the milk's nutritional benefits, but can alter the milk just enough so that homemade yogurt batches fail. The milk doesn't need to be an expensive brand. I only use house-brand milk, this recent batch the house-brand from a different store.

After I had success with this recent batch, I found other folks had similar experiences with failed batches, one brand of milk worked, another didn't.

I'm sure you're curious about what I did with the failed batch of yogurt. I ate it anyway, thickening it with soy milk powder before adding vanilla and honey. I suppose I could have used it in baking, making pancakes, or making cream soup. 

Anyway, just sharing my personal experience with changing brands of milk after a failed batch of yogurt.