I have many recipes that require an ingredient called "Greek Yogurt".  How is Greek Yogurt different from other types of yogurt? Is it widely available?

-- Ivonne

There are three major differences between traditional Greek Yogurt, called yiaourti in Greece, and what you find in most North American supermarkets.  Greek Yogurt may be made from sheep's or cow's milk.  It may be somewhat higher in fat content than standard yogurt.  And most importantly, it is considerably thicker.

Cuisipro Donvier Electronic Yogurt Maker

To start with, sheep's milk has a somewhat different flavor which some describe as tangy or nutty.  Raw sheep's milk contains as much as 7% milk fat, by weight, compared to about 3.7% for cow's milk.  In production, either the milk is boiled down to reduce the water content or the yogurt is strained to remove excess moisture, resulting in a product which is the consistency of clotted cream.  The decreased water content results in a higher still percentage of milk fat, as much as 10% for the final product.  Substituting supermarket yogurt for Greek Yogurt won't work in many recipes due to the excess liquid and runnier consistency.  If you have ever had tzatziki made from regular yogurt, you probably found it thin and watery.  On the other hand, tzatziki made with Greek Yogurt is thicker and smoother.

Greek Yogurt may be found in some specialty or ethnic food stores.  The Fage brand of Greek Yogurt is available in the United States, although I have not seen it in Canada.  Some local artisanal dairies and cheese makers may even make Greek Yogurt.

If you can't find Greek Yogurt where you live, you can make an acceptable substitute by straining supermarket yogurt.  To do this, I line a large strainer with a coffee filter, set it over a bowl and dump in a container of full fat regular yogurt.  I then cover the whole thing with plastic wrap and leave it in the refrigerator for several hours or overnight.  When done, the yogurt will have reduced in volume by about half, and there will be an equal amount of slightly yellowish liquid in the bowl.  The strained yogurt, which some refer to as yogurt cheese, can now be used in cooking.  I prefer full fat yogurt for three reasons.  First the added fat will make it more tolerant to cooking.  Second, some flavors are fat soluble and therefore are better distributed in a full fat base.  And finally, the added fat improves the mouthfeel of the finished product.