Getting Cultured: Yogurt

My grocery store had a sale on milk the other day, but the expiration dates are coming up a little too fast. I made a batch of hot cocoa, a pot of tapioca pudding that disappeared in no time, and still there was plenty of milk in my fridge.

But, behold! There was also a partial tub of plain yogurt! What are the odds? I hadn't made yogurt in... years? But I already painted a hallway this week. And sorted out tubs of toys to give away. I attended a screening of a new feminist film last night, and I was feeling courageous this morning.

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So... I poured a half gallon of milk (2%) into a big pot, whisked in a cup of powdered milk for extra body and protein (please don't ask how long that box has been sitting in the back of my cupboard), and heated it till the surface got bubbly (180-190 F). I took it off the heat and let it cool to 110 degrees. I decided I want my kids to enjoy this batch too, so I went ahead and added some sugar and about a tablespoon of vanilla.

When the milk was cool enough, I scooped a cup of plain yogurt into my blender, and added a few scoops of the warm milk. I mixed it on a slow speed till the yogurt was well blended in. I added some more milk and blended it again. Then I poured the mixture back into the pot of milk and whisked it all together.

I turned the oven on at the lowest temperature (150?) and set some clean jars on the oven rack to warm while I got out some clean lids. Then I ladled the warm milk into the warm jars and stuck the jars back in the oven*, which I turned completely off.

I left the light on inside, partly because it releases just a tiny bit of heat, and partly so I wouldn't forget the yogurt till tomorrow morning. Because I would do something like that. Like the leftover corn that sat in the microwave overnight instead of making it to the dining table the other night. Yeah. I want my yogurt cultured, not decayed.

I popped the jars in the oven before rushing out to my kids' school this afternoon, and literally pulled them out on my way out the door headed back to their school after dinner. In the warm oven, the yogurt was ready in just four hours.

I've been doing some reading on the science/chemistry of yogurt, and I want to experiment with different temperatures next time. I took my first course in biology last spring, and am now more curious than ever about the magic that happens in my kitchen.

I mean, seriously. What kind of magic makes this possible??




*If you need your oven for other things, you can also grow your yogurt in an insulated picnic cooler. Find a spot where it won't be jostled or disturbed while the yogurt works its magic. I usually add two extra jars filled with hot tap water, just to help maintain an even temperature. Nestle them between the jars of milk, close the lid, and wait.