Homemade yogurt: batting .500

Yesterday we succesfully made homemade yogurt. We used a simple recipe based on the one in The Tightwad Gazette, by Amy Dacyczyn:

1. Mix a quart of milk with 1/2 cup dry milk powder.
2. Heat to 180 degrees F.
3. Cool to 115 degrees F.
4. Whisk in 2 tbsp store-bought yogurt with live cultures.
5. Incubate at 110 degrees F for 4-8 hours.
   

A few days ago we made a valiant first try that utterly failed. Following Dacyczyn's advice, we used a heating pad on "low" to keep the yogurt warm during the incubation step. However when it was finished Amanda noticed that the yogurt was at room temperature -- not 110 degrees. And, I completely forgot to add the milk powder. The result was a batch of milk with a slight sour taste. Ooops.

Yesterday we tried again, but this time I remembered to add the powder, and we set the heat pad on "high." This batch turned out to be actual yogurt! It was a little runnier than store-bought, but in retrospect I had doubled the amount of milk but forgot to double the amount of dried milk. I plan on using the prescribed proportion of milk powder next time, which I think will yield a thicker consistency.

At our grocery store, organic milk costs $3.50/half gallon (5.7 cents/oz), and generic plain yogurt costs $2.79/32 oz (8.7 cents/oz). We typically use about 40 oz/week, so making our own yogurt saves about $1.20/week and gives us an "upgrade" to organic. Not a huge sum, but a buck's a buck. There's also a convenience factor, since the store containers never last the whole week, but we can make a homemade batch in whatever size we want.