I have a recipe that calls for plain yogurt.  I don't have any but I do have plain greek yogurt.  How do I substitute greek yogurt for plain yogurt?  Do I use the same amounts or do I need to add more or less greek yogurt?

--Mellisa

Real greek yogurt is usually higher fat and has less water content than regular yogurt.  It may also be made with sheep's milk rather than cow's milk.  Regular plain yogurt, not low-fat or skim, has around 3¼% fat by weight, according to the USDA Nutrient Database.  While they don't appear to list greek yogurt, it can be upwards of 7%.  In fact, I have a container of greek yogurt right now that says it is 11% milk fat by weight!

Water is removed from greek yogurt by either straining the yogurt or reducing the water content of the milk by boiling, sort of like making evaporated milk, before production.

Greek style yogurt may be more like plain yogurt, but with additional thickening agents to change the consistency to something more like real greek yogurt.

I have previously described the differences between plain and greek yogurt here, and explained how you can make an acceptable substitute for greek yogurt by straining plain yogurt.  In that case, somewhere around ⅓ to ½ of the total volume is strained off as whey.

So, depending on what your recipe is for and what kind of greek yogurt you have, substituting in the opposite direction may or may not work.  In some recipes, you can just use greek or greek style yogurt directly in place of  regular yogurt, although if it is made from sheep's milk, you may find the taste slightly different.

In some baking applications, you may be able to substitute greek yogurt diluted with either water or skim milk without problems, but the increased fat content may be an issue.  To try this, for each cup of plain yogurt called for in the recipe, try substituting ⅔ of a cup of greek yogurt mixed with ⅓ cup of water or skim milk.  If the result is too dry, add a bit more liquid.  It may take some experimentation to get the right proportions.

If the recipe is for cookies, though, you may want to reduce the other fat used in the recipe by about 1½ teaspoons per cup of yogurt called for in the original recipe as the higher fat content may change both the texture and spread of the cookies.

If you are using greek style yogurt, you can try diluting it as above, but the added thickening agents, if any, may affect the end result.