I've been making yogurt now for about two and a half years. My wife experimented with the Specific Carbohydrate Diet a couple of years ago and we liked the lactose free yogurt methodology that it recommends. You can buy lactose free yogurt in stores, but I like the thickness and taste of the home made stuff.
SCD lactose free yogurt is "cooked" for 24 hours (regular yogurt is only left to ferment for about 4 hours). You probably need a yogurt maker to be able to control the temperature for 24 hours. An cooler or oven is not going to be convenient.
We got a Yogourmet yogurt maker and have been very happy with it. They only change that we made was that we use a glass jar instead of the plastic vessel that comes with it. We bought the jar from Lucy's Kitchen in Bellingham. We also bought a voltage dimmer in case we needed to increase or decrease the temperature of the yogurt maker because our house is on the cold side and we were concerned that the temperature might end up being a little low. The temperature turned out to be very stable and at exactly the right level (110 degrees).
We've been using the Yogourmet yogurt starter as well (since it is recommended by the SCD for lactose free yogurt), but I'm going to get some heirloom yogurt cultures from Cultures for Health soon and try them. The Bulgarian starter may be where I start.
This is how I make my yogurt.
Step 1
Make sure all your gear is washed/clean. I also pour boiling water over all my pans, jars and spoons. But I don't boil them for 5 minutes.
Gear
Sauce pan
Metal spoon
1/2 cup metal measuring cup (plastic is fine too)
Thermometer
Fermenting jar with lid
Step 2
Bring your milk up to temperature. If you are using raw milk, you need to bring it up to 180 degrees and then bring it down to 110 degrees. If you are using pasturized milk, you can just bring it up to 110 degrees and you're done. I use goat milk, but I've used homogenized cow milk and had the same good results. Stir the milk while you heat it.
Tip
I pull the milk off the burner at about 106 degrees. The pan continues to transmit heat and the temperature will climb. Experiment and find out what works for your pan and range. Cooling the milk off takes time. I use a large bowl with ice water in it for cooling down 180 degree milk (and I stir it).
Step 3
Put your yogurt starter in your fermentation vessel. Then pour a couple of cups of 110 degree milk into your vessel and stir it to mix the milk and starter. Then pour the rest of the milk into your vessel and put on the lid.
Step 4
Put your vessel into your yogurt maker. Make sure to follow the maker's instructions. The Yogourmet maker requires warm water to fill the void between the fermentation vessel/jar and the maker container. The water level ends up being about the same as the milk in the jar.
Step 5
Plug in the yogurt maker and let it sit for 24 hours.
Step 6
The fermented milk will likely be a little runny. More like kefir. You can make it thicker by adding milk solids to the milk before "cooking" it. But the Yogourmet maker comes with a cheese cloth bag and that's what I use to thicken up the yogurt. I pour the yogurt into the bag and hang the bag above a bowl for about 12 hours to strain off the whey.
Tip
I use the whey to bake with. I usually make muffins and bread with it.
Step 7
After 12 hours or so I empty the bag of yogurt into a container. I also scrape all the yogurt off of and out of the bag. I try not to waste any. It's very thick at this point... pretty much Greek yogurt. If you like your yogurt thinner, strain it for less time. Or stir a little whey back in.
Tip
Straining the whey off for about 12 hours pulls about half of the volume of the yogurt out as whey. I start out with 64 fluid ounces of yogurt and end up with about 32 ounces of thick yogurt and 32 ounces of whey. Different cheese cloths will likely result in different results.
Update
I have been looking into using heirloom cultures and have learned that the 24 hour culturing time stresses the bacteria to the point that the resulting yogurt can't really be used as a starter for a new batch of yogurt. CulturesForHealth.com has a good page about this. They suggest keeping a mother batch of yogurt to use as a starter for the 24 batches.
