From a GardenFork Fan, an easy way to make yogurt using your oven. You don't need special equipment, its easy to make, here's how. Below this yogurt recipe are links to our how to make yogurt videos and more fermentation stuff.
I recommend one special tool; a probe thermometer with an alarm that notifies you when your food has reached the desired temperature. I use this one. There are lots of them on the market ranging from $15 to $60. However any thermometer that will read from 100 to 200 degrees will tell you what you need to know.
Tish's Easy Way To Make Yogurt Recipe:
Warm your milk in a non-reactive pan over moderate heat to 180 degrees Fahrenheit. go slowly with this step for two reasons. First you don't want to scorch the milk and second, slow warming allows for some evaporation of water in the milk and that makes a thicker, creamier yogurt. The probe thermometer is a big help here because you don't have to stand over the milk and stir it. I set this up when I have other kitchen jobs to do and give the pan a quick stir every now and then.
Once the milk has reached 180 degrees, you can hold it there for more evaporation or remove it from the heat right away. You do not want your milk to boil. Allow the milk to cool to 110 degrees (re-set your programmable thermometer to alert you when the milk has cooled). Spoon some of the warm milk into your yogurt culture and stir it in. Keep stirring in milk, a spoonful at a time, until the mix is smooth and thin enough to blend easily with the full pot of milk. Add the culture to the milk in the pot and stir it thoroughly. Pour the cultured milk into your clean containers and cover the containers.
Many ovens can maintain a perfect temperature for yogurt, just by keeping the oven light on. Before you begin, test this by leaving the oven light on for several hours with the probe thermometer sitting on the rack. If the bulb keeps your oven at 100 to 115 degrees, you've found your yogurt machine. If this doesn't work, use a personal sized cooler - the ones designed to hold one or two six-packs of drink cans. Wash the cooler out with hot tap water, even if it's already clean because you want to warm it. Set the containers of cultured milk in the cooler, add enough hot tap water to come right up to the tops of the containers, cover and move the cooler to a quiet spot in the kitchen.
Leave your yogurt alone for 8 to 12 hours then move it to the refrigerator. Enjoy!
I use pasteurized milk. Many national brands of milk are now ultra-pasteurized and I don't know how that will do for yogurt. It won't make cheese so I haven't tried it with yogurt. You can use any fat content you like from whole milk to skim.
You can buy yogurt culture from New England Cheesemaking. I have done that. However I have had really good results using plain yogurt from the grocery store. In the past I have had problems with the flavor of the yogurt (made with grocery store starter) changing from batch to batch but for the last year that has not happened. Any unflavored yogurt with live cultures will do, but I use the Giant grocery store house brand. Look for live cultures and an ingredient list that includes no more than three items (Milk, live cultures, and maybe milk solids). You need about a tablespoon per quart of new milk.
If you like your yogurt thick, you can add non-fat dry milk to the milk while you warm it. I add a lot - a cup of dry milk per quart of new milk. This gives me yogurt that is almost like Greek yogurt. I get very little whey separation with this much added milk.
I warm my milk while I fix dinner, cool it while I eat, and leave it in the little cooler overnight. I make two quarts every ten to fourteen days.
I just want you to know that you don't need expensive tools or yogurt-specific equipment. Yogurt is a simple food and it's easy to make.
Listen to Sandor Katz talk about fermentation, how to make sauerkraut and yogurt on GF Radio here.