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There are lots of instructions for homemade yogurt out there. I developed one that I think is somewhere in between too-casual-I-can-tell-this-might-not-work and too-scientific-I'm-not-buying-a-heating-pad. Find the recipe that feels right to you and hopefully you'll have great success.
(p.s. This instructables version is better than the version on my blog, but I always include a link just in case you feel like visiting.)

You'll need:

- 1/2 gallon of whole or 2% milk that is not Ultra-Pasteurized (This has to do with the temperature it was pasteurized at. If milk has been Ultra-Pasteurized it must be labeled that way, so it's generally easy to avoid. The only organic milk I've found in my neighborhood that will work is from Trader Joe's)
- 1 small plain, all-natural yogurt that has live cultures (like Nancy's)
- thermometer
- slow cooker or double-boiler
- small bowl, stirring spoon, and ladle
- an oven or closed space that you aren't going to need for 8 hours
- towel
- tea-kettle or pot with lid
- butter muslin or cheese cloth if you like thick (Greek-style) yogurt
- optional fruit to stir in

Step 1: Sanitize Your Equipment

Clean all the equipment you'll use very well, being sure to get all the soap residue off. Just to be sure, I like to boil a pot of water and dump it in my slow cooker and the bowl. Then I swish a stirring spoon, ladle, and the thermometer in the hot water. You want to avoid adding any other bacteria to the milk so that you can just cultivate the good, yogurt bacteria.

Step 2: Heat the Milk to 180 Degrees

Heat the milk to 180 degrees in the slow cooker on high (or in a double-boiler). It takes my slow cooker about an hour and a half, but it needs very little attention through this stage.
I tried skipping this step once because it's basically just to kill whatever bacteria might be in the milk (my reasoning was, I just specially bought non-ultra-pasteurized milk, why would I heat it up so high now?), but the yogurt didn't work. It was really sticky and separated and not yogurt-sour, but strange sour.

Step 3: Cool the Milk to 110 Degrees & Add the Yogurt Starter

Turn off the heat and let it cool to between 100 and 115 degrees. This takes about 1/2 an hour to an hour. It goes faster if you stir.
In a clean bowl combine the store-bought yogurt with 1 cup of the warm milk and mix well. Add this yogurt mix back to the slow cooker.

If you add the yogurt starter when it's too hot you'll kill the bacteria, cook the yogurt, and it won't combine. If this happens (because maybe you were excited and trying to skip steps) you can strain out the cooked yogurt (I thought it tasted kind of good), let the milk cool, and add more starter yogurt.

Step 4: Keep the Yogurt Warm and Undisturbed

Wrap the slow cooker (lid on) in a thick towel and put it in the oven with the light on.
Boil some water in the tea kettle or pot and put that in the oven too. This keeps my oven at a perfect 100 degrees.
Let this sit undisturbed for 6 to 12 hours, depending on how tangy you like your yogurt. I do 8 hours.

Step 5: Now You Have Yogurt!

Ok, now you should have yogurt! Put it in the fridge to stop the fermentation process and help it firm up. If you have a lot of yellowish liquid floating around, don't worry, this is whey. You can stir it back in or, if you're going to strain your yogurt, just leave it.
If you think you might make another batch, save about 1/2 a cup for the next time instead of using a store-bought yogurt.

Step 6: Optional: Strain Yogurt to Thickens

You can be finished now, but I like thick yogurt so I line a colander with a square of butter muslin and scoop yogurt into it, then pick up the four corners and tie it into a little hobo bundle (this batch had to be divided into 3 bundles). I hang my yogurt over a bowl for about an hour before mixing in sugar and fruit.

Step 7: Optional: Add Fruit and Sugar

I make a quick "jam" while the yogurt is working in the oven. For a batch this size I cut up about 5 cups of fruit and simmered this on low for about an hour (until it was syrupy) with 1 cup of sugar and the juice of half a lemon. Be sure to let it cool before adding it to your yogurt.

ps - I read that it's not a good idea to add honey to yogurt if you're going to store it in the fridge because the honey bacterias can kill the yogurt bacterias. Add honey to each serving right before you eat it. If anyone knows more about this, let me know.

<p>Regarding the honey killing yogurt bacteria - if that's true, why would Noosa sell a yogurt with honey in it - http://www.noosayoghurt.com/product/honey/...and some people say this is the best store-bought yogurt they've had...?</p>
That's because you are not just heating the milk to kill off other bacteria, but to denature the protein - you will get thicker yoghurt this way, though it is possibly to make yoghurt without this step, and even with raw milk.
<p>This is almost the same recipe I use to make yogurt using a sous-vide water bath, which can control temperature to within +-1 to 2F. Certainly, this kind of precision is not needed, but it is a nice secondary use if you should happen to have this setup. I process in mason jars, and they sit in a water bath, and so you can start the water bath with hot water from the tap, and then it doesn't take that long to get up to 180F. I hold it at 180F for 1/2 hour, but I think 10 minutes is probably plenty. And then you can use ice to bring it down to 110-115F.</p><p>If you use whole milk, as the milk cools, it will form a milk skin, or lactoderm. (No, I didn't know what word, I just found it on Wikipedia, LOL!) If you ever had hot cocoa as a kid and it was overheated, you are familiar with it. You probably went &quot;yuck!&quot; But this makes a nice little variation in the yogurt texture, if you can avoid disturbing it. You will have an extra-yummy layer at the top. You probably will not get this with 2% or less milk, only whole.</p><p>So, I use a turkey baster to carefully remove some of the milk for mixing with the starter, and then use the turkey baster to re-inject it. You do not need to mix it up much, in fact I have seen many recipes that suggest only a bit of gentle mixing. I find that injecting with the turkey baster is perfect. I suppose it should be obvious, but it is best to keep a special turkey-baster for this!</p><p>As well, if you use cream-top milk, all the better. Mix it up as best you can, and some cream will go to the top as it is culturing, and you get an extra-special bit at the top of the jar.</p><p>With the sous-vide setup, you can culture for an extended period of time without worrying about temperature control. I've been going 18 hours. Yogurt culture is pretty un-picky, though. In the 70's my hippy neighbor made it wrapped-up in towels on the radiator.</p>
Your instructions are very good. My two cents: <br>For those of us who are into decimal... 180 Fahrenheit equals 82,2 celsius, and 110 Fahrenheit are 43,3 celsius. Also, 1/2 gallon is 1,92 liters. <br>It is correct that honey has antiseptic properties, but it also should be remembered that it is not to be given to babies (some recommend to nobody under 3 years of age) due to the possibility of the natural presence of botulinum endospores in honey. As wiki rightly says: &quot;The more-developed digestive system of older children and adults generally destroys the spores. Infants, however, can contract botulism from honey&quot;.
I made your yogurt without a thermometer but followed your time guidelines. It turned out GREAT. One hint, I did not want to use any more electricity so I put the crock pot into the oven with two tea lights lit on the very bottom. Worked! <br>Just make sure there is nothing hanging down that could catch fire. <br>Thank you.
Honey actually has antibacterial/ antiseptic properties http://en.wikipedia.org/wiki/Honey#In_medicine
I've heard that too, but yogurt bacterias do not like honey.
yes because honey is a antibacterial agent so it kills bacteria
Oh funny, I totally misread your comment. Good point - both times.
Great instructable!&nbsp;Im definately going to make yogurt some day.<br /> <br /> Regarding the honey, to make yogurt last, it's probably best to not add anything, as any change in composition (additon of sugar for example) will benefit a slightly different set of bacteria compared to the original yogurt. <br />
I've tried it now with sugar and fruit mixed in and after two weeks it was still great. I think I won't push it with the honey though because I know you're right about adding different bacteria.<br />
After adding the starter, I wrap it with a few coats so it is nice and thick and let it sit on kitchen table for 4 hours. This usually produces a yogurt that we like. The idea is to cerate a habitable environment for bacteria. This would save you the oven and warm water steps. We also boil the milk first and let it cool down by itself.<br />
I haven't had luck with only 4 hours for how thick and tangy I like my yogurt, but I've seen that in other recipes. Great idea with the coats. I don't have a ton of space in my house so tucking it all away in the oven works great for me.<br />
Yum! Sounds easy &amp; delicious! Can't wait to try it out.<br />

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