Make Yogurt Without an Incubator
================================

You can make yogurt at home without any special incubator.  Making
yogurt involves taking milk and a culture and keeping warm at the
temperature the yogurt culture likes.

You don't need to mail order yogurt cultures, either.  When shopping
in the supermarket look on the back of yogurt containers in the
ingredient list for **"contains active cultures"**.

This means you can take a few tablespoons of the store yogurt
and make *gallons* of yogurt for only the price of milk.

Ingredients
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![Milk and left-over yogurt](pics/sm/milk-and-culture.jpg)

* Gallon of whole milk
* New or left-over store-bought yogurt

Whole milk, compared to skim milk, will give a thicker and richer flavor.
You can use skim milk, but the yogurt won't be as thick and it will be
a bit more tart.

The tartness/acidity of whole or skim yogurt is the same, but you notice
it a lot more with skim milk.

Check for "active cultures"
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![Make sure label says active cultures](pics/sm/active-live-cultures-label-zoom.jpg)

(optional) Pasteurize Milk
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If the milk was not pasteurized, do so now and then cool the milk to 110 degrees.

Add some yogurt starter/culture to milk and stir
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![Scoop out Yogurt](pics/sm/scoop-out-yogurt-culture.jpg)
![Stir yogurt culture and milk](pics/sm/stir-culture-and-milk.jpg)

Take the last of your left-over yogurt and stir it into the milk.

Once stirred in you should avoid stirring or agitating the milk because
it will separate the yogurt and whey.  This is more important towards
the end than the beginning.

Heat Milk to 110 Degrees Fahrenheit (43 Celcius)
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![Heat milk and yogurt to 110 degrees](pics/sm/warm-to-110-degrees-zoom.jpg)

Yogurt cultures work best at 110 degrees Fahrenheit.

Keep the milk/yogurt warm
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![Warm oven slightly](pics/sm/warm-oven-slightly.jpg)
![Place pot in oven](pics/sm/place-yogurt-in-oven.jpg)

Keep the milk/yogurt warm (around 110 degrees (43 C)) for 4-7 hours.

You want to maintain this temperature reasonably well.  An 
incubator will keep it at exactly the temperature, but the good
news is that a hot pot of liquid will hold its temperature for
a long time.

You can try wrapping it in blankets, or having a hot water
bath that you change the water from time to time, but I've
found using an oven works very well.

Turn the oven on for a few minutes, just enough to make it
*warm* in the oven, then turn it off.

Ovens are well insulated, so by starting off in a warm state the
pot of yogurt will not lose much heat at all.

Every hour or so you can briefly warm the oven up.

### Touch the pot to feel how warm it is

Right when you put the pot in the oven, feel the side of it
to get an idea of how 110 F (43 C) degrees feels.

You can use this as a test when you go to warm the oven up
occasional.

Even if the pot cools off to 100 F (43 C) degrees, it will still works
but may take longer and it won't be as thick.

### (Optional) More time == tartness

Leave the yogurt in the oven for more than 7 hours.  This will
result in a more tart yogurt.

I usually start my yogurt in the evening, monitor the temperature
for a couple hours, then leave it as-is over night.

Cool and store the yogurt
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![Finished yogurt](pics/sm/finished-yogurt.jpg)
![Store yogurt in quart containers](pics/sm/store-in-quart-container.jpg)

Cool the pot in the refrigerator for a few hours and then
portion out into quart containers.