In the Kitchen‎ > ‎Basics‎ > ‎

Yoghurt

Yoghurt is an interesting thing to make.  It can be about as simple or as complicated as you want. 

The very simplest method is: Heat 1 qt milk to 116°F, add ¼ cup of yoghurt to it, and keep it warm for 8 hours.  And that's all there is to it... if you want a lumpy yoghurt with a snotty consistency. 

Below is the recipe i use, which is much smoother, creamier, and more delicious:

1
qt
milk

c
non-fat dried milk powder (optional)
1
pkt
yoghurt culture OR
¼
c
yoghurt (from your last batch)
  • Pour milk into a double-boiler (or just a pot inside another pot filled with water) and start heating. 
  • When milk reaches 110°F, ladle out a bit into a bowl and add your culture to it.  If you are using yoghurt instead of culture, you'll need a little more - just enough to mix with it to warm it up and make it liquid again.
  • When milk reaches 120°F, add non-fat dried milk powder.  This is optional, but it makes the final product firmer and smoother.
  • Keep heating, stirring fairly regularly, until milk reaches 180°F.  Reduce the heat enough to keep the temperature at 180 for 20 minutes. Do NOT let it boil.  If it boils, throw it out.
  • After 20 minutes, remove the part of the double-boiler containing the milk and cool it rapidly to 120°F.
    • If you're doing this during the winter, the best way is to just grab it, drag it outside, and stick it in a snowbank, stirring constantly until it reaches 120°F.
    • Otherwise, a larger pot full of ice water will do in a pinch, but is not nearly as much fun.
  • Very gently and gradually, ladle out spoonfuls of milk into the container with your yoghurt culture.  Once you've got a cup or more in the container, pour the container back into the pot with the milk and stir it in thoroughly.  (This step didn't make a lot of sense to me when I first started making yoghurt, but it does make a difference.  Just dumping it into the milk without gradually acclimatizing it to the warmth can "bruise" your culture.)
  • Pour the milk into ½pt canning jars and put them in your yoghurt maker.  Or, if you're making a bulk batch, just pour it into your Yogo-therm, or whatever you're using.  If you don't have a yoghurt maker, get one - it sucks making this without one.
  • Let the yoghurt culture grow for 7 - 8 hours.  The longer it grows, the more sour, so if you're going to be cooking with it or if you're going to make a greek-style yoghurt, leave it up to 12 hours.  For desserts and very sweet yoghurt, 5 hours is about the minimum amount of time it takes to cross the line between milk and yoghurt.
  • The yoghurt will keep in the fridge for about 10 days.
I've made a lot of yoghurt over the years, and i've learned some important tips that i'll pass on to you here:
  • Don't use gelatin in your yoghurt.  It's gross.  Besides, it has a weird texture.  If it's not thick enough, use more non-fat dried milk powder instead.
  • If you're using yoghurt from your last batch, that's great, but after about 5 or 8 batches, think about getting some fresh stock.  Gradually, other types of cultures "move in," and they're not always tasty.
  • When stirring, make sure you don't stir hard enough to cause bubbles to form on top of the milk.  The science behind this is actually pretty cool: In milk, fat molecules are encased in casein, which is the protein that will make your yoghurt firm.  When you shake or stir vigorously (like when you make butter), it breaks the casein molecules apart, and the fat molecules separate... and you get butter floating on top of your yoghurt.  It's really not as good as it sounds.
  • You can use any kind of milk for yoghurt.  I prefer 1% or skim, just because you really don't need the full flavor of whole milk for good yoghurt like you do with other things.  In fact, you probably won't notice a difference.
  • If you have access to raw milk, that's great!  You don't need to worry about pasteurizing it, because the 20 minutes at 180°F are doing that for you.  However, oddly enough, homogenized milk does seem to make better yoghurt, and homogenization isn't really one of those things you just up and do in your kitchen, generally.  My apologies to my hundreds of years of dairy farming ancestors!
  • If you use goat's milk, you'll find that your yoghurt will not be quite as thick as with cow's.  
  • Don't worry if you see a little whey on top or around the sides of your yoghurt.  Just stir it in - it's good, and good for you!
  • The rapid cool-down process is essential for good yoghurt.  The longer it takes to cool down, the more of an off-taste it will have.
  • Temperatures over 120°F will kill the bacteria that turn the milk into yoghurt.
  • Yoghurt may contain many different types of bacteria, but the most common are:
    • Lactococcus thermophilus (a.k.a. Streptococcus salivarius subsp. thermophilus)
    • Lactococcus bulgaricus (a.k.a. Lactobacillus delbrueckii subsp. bulgaricus)
    • Lactococcus lactis
    • Lactobacillus delbrueckii
    • Lactobacillus acidophilus
    • Bifidobacterium spp.
  • Lactococcus is a synonym for Streptococcus.  Don't let this worry you - it's not the type that causes strep.  Almost all cultured dairy products (yoghurt, cheese, sour cream, etc.) contain a type of Lactococcus. However, cheesemaking scientists have changed the name for just this reason.
  • Most yoghurt cultures contain at least three or four of the bacteria above.
  • Cultures containing L. bulgaricus produce the best, creamiest yoghurts.
  • There are lots of places to buy yoghurt culture.  I get mine from the New England Cheesemaking Supply Company.
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