Now, I know what you're thinking ... This girl is CRAZY. She wants me to make yogurt at home? Why on Earth would I do that?! All I can say is this, I have a curious mind, sometimes it leads me in strange directions. Let me tell you though, this is probably the easiest recipe I'll ever post. It basically requires you to do almost nothing with two ingredients.
I started making yogurt a few years ago, when I began to get seriously interested in food. One weekend (when I was supposed to be studying for an anthropology midterm or something) I went down an internet rabbit hole and came across this blog post describing how easy and awesome making yogurt can be, not to mention how much cheaper it is. Being the olympic level procrastinator that I am, I pushed my text books aside and got started right away. When I woke up the next morning and discovered the pot full of yogurt that had miraculously appeared in my oven, I was amazed. It was like magic. It totally sparked my curiosity about fermentation, and ever since I've been trying to learn as much as I can.
I'm by no means an expert, but I'll do my best to explain some of the science behind the whole yogurt making process ... This is a little bit technical, but bear with me; understanding what happens leads to better yogurt, I swear. On the other hand, if you find this kind of stuff unbearable to read, no worries, like I said above, it works whether or not you know why.
You only need two ingredients: milk, and a tiny bit of yogurt! The most important thing is that you find a plain yogurt (no flavours or sweeteners) with active bacterial culture listed as one of the ingredients. The culture is what will turn the milk into the creamy, tangy yogurt you are after. It shouldn't have much else though: milk, active bacterial cultures, and maybe cream. Yogurt manufacturers often add other things, like gelatin, cornstarch, extra milk proteins, to emulsify and stabilize their products. These things are not really desirable, but I don't think they'll interfere with your yogurt considering we are using such a small amount.
There are two basic steps to making yogurt. The first one is pretty straight forward: heat up the milk until it is almost boiling, then let it cool partially, to about 105-110˚F. With a thermometer and some observation, this step is easy to control. Heating the milk kills any unwanted bacteria that might compete with your culture, it also allows some of the water in the milk to evaporate and gives the milk proteins a head start on coagulation, making for creamier, firmer yogurt.
The second step is the fermentation process. This is when you add your yogurt starter (the active bacterial culture), and let the mixture incubate until it sets. The bacteria that turn milk into yogurt are thermophilic, which means they need heat to do their job. Some people use crockpots or machines made specifically for yogurt to keep everything warm, but that is not necessary. You can use a preheated cooler, a thermos, or you can do what I do: the oven method. This method uses the heat from the oven light to keep the yogurt at a steady temperature for as long as it needs. The incubation temperature has a big effect on how long the yogurt takes to set and the final texture of the yogurt. The higher the temperature, the faster the process. However, a high temperature leads to a coarser, firmer yogurt which will separate more easily. A slow, low temperature ferment results in a creamier, more finely textured yogurt with a little bit more tang. The longer fermentation also allows the bacteria to convert more of the lactose into lactic acid, making it easier for us to digest.
