This is possibly the most boring post I've ever done, if you aren't into yogurt-making. But I feel the need to pass on some important discoveries I've made in the world of yogurt, for my 2 readers who care.
We go through a fair amount of yogurt. Vicki Jo loves to eat it straight (that's right - plain, tart, whole-milk yogurt. She begs for it!), especially in the morning while I'm fixing breakfast. I don't eat a lot of it plain, but use quite a bit for my yogurt dough crackers, yogurt dip, frozen yogurt, and smoothies. I'd say we eat between a 1-2 quarts per week.
I hadn't been getting enough raw milk through our co-op to make our own yogurt, but I was getting sick of shelling out to buy so much of it. So, I upped our order to 2 gallons of milk per week, and set about making yogurt once again.
I had experimented with making yogurt in the past, but had never found a good method. It always seemed to come out very runny - more like a pourable kefir consistency. It tasted great, but didn't have the body that I was looking for. I started asking around - emailing my favorite food blogger, inquiring on a great listserv - and here's what I found.
1) Raw milk presents a different set of issues than pasteurized milk when making yogurt. There are many enzymes and strains of beneficial bacteria present (that's why you want raw milk in the first place!), but these compete with the yogurt culture and don't allow it to come to its full strength. This is what produces the weak body of raw yogurt.
2) You have a choice to make: preserve the enzymatic activity and beneficial bacteria and have runny yogurt, or kill some of it off through high heating (180 F), and have the yogurt consistency you are accustomed to.
I did try a different method first: I put a teaspoon of gelatin powder into my warm milk when making raw yogurt, in an attempt to firm up the consistency without having to heat the milk too high. It thickened the yogurt beautifully, but it produced a wobbly, pudding-like mouthfeel that I found unpleasant to eat. It did make really nice, pliable frozen yogurt, but the protein from the gelatin made it impossible to strain the whey out for dip. So, for what it's worth, and for what you use your yogurt for, you might try gelatin.
Here's what I've been doing now:
1) Heat a scant 1 quart raw milk to 180 F.
2) Stir in 2 T plain, whole, storebought yogurt (it's important to have a pure seed starter like storebought yogurt to introduce the proper strains of bacteria. If you culture from your own batch over and over, without introducing an independent starter, you might cultivate the wrong strains over time and have a wonky product).
3) Pour into a quart-size mason jar and cap tightly.
4) Submerge in the ceramic liner of your crock-pot, which you have filled with 110-degree water.
5) Place the lid on the crock-pot, place it in your oven, and leave it in there with the light on.
6) Allow to culture for 12-24 hours.
7) Refrigerate to finish setting the yogurt.
I hope this helps other raw-milk enthusiasts who are having trouble getting yogurt to the consistency they would prefer.