Monday, January 10, 2011

Home-Made Greek Yogurt, Part I

     I don't like regular yogurt but I love Greek yogurt for several reasons.  It's thick and creamy--see how it stuck to the spoon in the picture above?  The taste is also more complex, being tangier and slightly less sweet than regular yogurt.  I decided to make this yogurt at home because it's expensive to buy and the process to make yogurt at home looked easy.  I'm happy to report that making Greek yogurt was very easy, but it did take a lot of time.

     On a side note, in Greece this kind of yogurt is actually called "strained yogurt," because that is how it is made.  Regular yogurt is piled into a cheesecloth and the liquid (or whey) is strained off over several hours.

     This was definitely a weekend project.  The entire process, from milk- to- strained yogurt, took 12-18 hours.  However, most of that time was "hands-off."  The majority of the work was in the very beginning, when I was preparing the milk to be cultured.  After that, I only needed to check on it every 30 minutes to make sure the temperature was in the correct range for the culturing to occur. Culturing milk needs to be done at a specific temperature range, 110-115 F, otherwise the live cultures in the yogurt (i.e. the "good" bacteria) die from the heat.

      The ingredient list for home-made yogurt was blissfully short: milk (use any fat content), powdered milk, a bit of commercial yogurt to use as a starter, ice-water, and plenty of time.  Regarding the milk, a high fat content will produce thicker yogurt but since I was straining it anyway, I decided to use skim milk.  The addition of powdered milk also helps to produce a thicker yogurt.  I decided to add it, despite the fact that I was straining it, because I had a box of powdered milk that I needed to use up.  I read that yogurt can be made without powdered milk but the consistency is thinner than what most people are used to as compared to commercial yogurt.  I was briefly concerned about using regular cow's milk--I have a mild lactose intolerance but I don't have a problem with commercial yogurt (obviously).  However, I wasn't sure if making the yogurt at home would "eat up" enough of the lactose sugar in the milk such that I could eat it without a problem.  I decided to go ahead since I didn't have a problem with commercial yogurt.  Thankfully, I didn't have a problem with my final product!

     In regards to using the commercial yogurt as a starter, I decided to use yogurt with several strains of live cultures. (It's really bacteria but bacteria has such a negative connotation.)  This was important to me because eating yogurt helps keep the balance of "good" bacteria in the gut, and I wanted as many strains of "good" bacteria as I could get!   I wanted to use Chobani Greek Yogurt because it has five live yogurt cultures but Kroger didn't have the plain flavor in stock that day, so I bought the Oikos Organic Greek Yogurt instead.  Oikos is made by Stonybrook Farms and it has three live cultures.  

     Now to culture the milk.  I needed to create a water bath; this is essentially a container inside of a container.  The outer container holds the water, thereby bathing the inner container.  I also needed a container that would maintain a temperature range of 110-115 F.  I read on the Internet that I could use my oven or even a heating pad but I didn't want to tie up the oven and I was using the heating pad for other purposes.  That's when I decided to use the slow-cooker to create the water bath.   It worked beautifully.  Slow-cookers take a while to heat-up, so I filled it with an inch of water and inserted the inner container, which was a glass loaf pan in the picture.  I then set the slow-cooker to WARM.  I let it preheat while I prepared the milk for culturing; that process took me an hour, which was the perfect length of time for the slow-cooker to warm up.

      When making yogurt, I needed containers that were non-porous: metal, porcelain, or glass.  These materials are easy to sterilize.  I didn't think that plastic would survive a dip into a boiling pot of water or a 100-plus degree water bath for 4-6 hours.  The first time I made this yogurt, I used glass baby-food jars.  They were six ounces each and they made perfect serving sizes for yogurt.  This recipe needed 6 jars to hold everything.  For my second round, I used a glass loaf pan since I was going to strain the yogurt.  It was much easier to empty the yogurt from the loaf pan than from the little jars!  Home-made yogurt is freeze-able and if you do so, you have to remember NOT to freeze any glass containers!  They'll crack.

Once the milk was ready to be cultured, I poured it into the inner containers (I used a funnel to fill the baby food jars without spilling).  Then I added additional water to the bath so that the top of the water came to the top of the milk in the containers.  You can kind of see it in the picture.  I discovered the hard way that empty glass containers float and tip over in a water bath that's too full. 

And that was it.  I set the lid of the slow-cooker ajar because the water bath got too hot otherwise.  The lid on my slow-cooker has a tiny opening for a probe and it happens to fit my meat thermometer perfectly.  If you look carefully, you can see that the tip is in the water bath, right next to the loaf pan.  I checked it every 30 minutes to insure that the water bath was the right temperature; I turned the slow-cooker off or to WARM to adjust accordingly.  The length of time to culture the yogurt depended on the kind of containers I used but it generally takes 4-6 hours.  The loaf pan needed 5 hours; the baby-food jars only took 4 hours.  I had read that one should not disturb milk in any way while it is culturing; it will make runny yogurt.  I took that to heart!

At the end of 4-6 hours, the yogurt didn't look different from the milk... 

   ...except when the pan was tilted.  Look, it didn't move!  It was definitely yogurt!

Home-Made Plain Yogurt In the Slow-Cooker
Inspired by Home-Made Plain Yogurt Recipe at

Yield: 1 quart

1 quart skim milk
1/4 cup non-fat dry milk powder
ice water, enough to fill a large mixing bowl about 3/4 full
3 tablespoons plain yogurt with active cultures

1.  Preheat the slow-cooker by turning it to WARM or LOW (whichever is the lowest setting on your slow cooker).  Fill with enough water so that the depth is 1 inch.  Insert the sterilized containers you will use to hold the milk for culture.  Suggestions include glass baby food jars or a glass loaf pan. 

2) Heat the skim milk over medium-low to medium heat until it starts to steam and the temperature reaches 180 degrees.  Stir the milk constantly while you heat it so it does not burn on the bottom.  The milk will reduce slightly.  Add the non-fat dry milk powder and stir to mix completely.

3)  Place the bottom of the pan in the mixing bowl full of ice-water.  Make sure the bottom of the pan is immersed in the ice water.  Add more ice water if needed.

4) Constantly stir the milk mixture and monitor the temperature of the liquid as it drops.  Once it is between 110-115, take it out of the ice-water.  Scoop out a cup of the warm milk and mix in the commercial yogurt.  Mix the yogurt completely into the milk then return the milk to the pan and stir it in completely.

5) Carefully place the yogurt container in the water bath.  Add more water so that the water is level with the top of the milk mixture.  Lightly cover the water bath and monitor the water temperature so that it remains between 110-115 Fahrenheit.  Turn the slow-cooker on or off as needed.  Culture the milk mixture for 4-6 hours.  It is done when the top of the yogurt is firm to the touch or when it doesn't move when the container is tilted slightly.

Nutrition Information Per  8-Ounce Serving*:
Calories: 110, Fat: 0g, Cholesterol: 0mg, Sodium: 160mg, Carbohydrates: 15g, Fiber: 0g, Sugars: 15g, Protein: 10g, Calcium: 40% RDA. 

*The nutrition information is actually for the commercial yogurt that I used for as my starter, the Oikos Greek Yogurt made by Stonybrook Farm.  I couldn't figure out a way to get the nutrition information for my home-made yogurt so I decided that the commercial nutritional information would be close enough.


  1. This is a great post with lots of info! I've heard about yogurt in the slow cooker. Inspiring. :)

  2. Hi Beverly,
    I'm so glad that you liked the post! Please share your experience with me if you decide to make the yogurt!


  3. You are a lady of many talents. I am very impressed! Looks delicious.


  4. Hi Nancy,
    Thanks for your comment and for checking out my blog!