Kitchen Science: Homemade Yogurt

I've been thinking in general about science lately and the ways in which I am curious about the sciences. Although in my career I've been exposed to a huge amount of information related to technology, my personal draw to the sciences tends to come more from the things I can do in my home that affect my real life.

In other words, my idea of doing a science project might look something like this:

Photo borrowed from eHow.

I always have a bunch of little experiments going on around the house. What happens whey I try to germinate seeds on a damp coffee filter? Can I create a concoction from baking soda, salt, and water that will unclog my sink? How much heat can a few baked potatoes wrapped in foil emit if I place them around a metal pot that I want to keep warm?

Over the weekend, I made yogurt from scratch, which is nothing short of a science project. The ingredients and steps are extraordinarily simple.

Ingredients: milk and yogurt.

Steps: Heat milk to 180º F. Cool milk to 110º F. Add a few tablespoons of yogurt. Keep warm for 7 or 8 hours. Strain.

It's an experiment that I want to try a few more times because I was not entirely pleased with the results.

First, I used a bain-marie to heat the milk, but I think it was unnecessary. Second, I used a half gallon of 2 percent milk and about 3 tablespoons of low-fat Fage Greek-style yogurt. Next time I will use less milk, and I'll use plain Dannon yogurt, which many bloggers recommended as a starter culture. Once you've made your own yogurt, you can reuse some of your own as the starter culture.

To keep the yogurt warm for several hours, I left it in an oven that had been recently warm from baking sweet potatoes and beets. I placed the still-warm vegetables, wrapped in foil, next to the metal pot to help keep it warm. Although I thought the oven-and-baked-potatoes method would be sufficient, I have a feeling this was the step that needs the most improvement. After seven hours, I checked the yogurt, and it had barely thickened. So I re-warmed the bain-marie to about 110º F, set the metal yogurt pot in there, and left it alone over night, for another seven hours. In the morning, it had thickened a bit more, but I have a feeling the temperature had dropped too soon.

One trick that I have read over and over is to use a heating pad, the kind people use for backaches, and set it under the yogurt pot, which is swathed in a large towel. I don't own a heating pad, and I don't really intend to buy one (I already had to purchase a cooking thermometer), so I'll have to think of some other crafty way to replicate the results.

The final step, draining the yogurt, did significantly improve the thickness, but it still wasn't quite to my liking.