Traditionally, Greek yogurt is a strained yogurt. It is a concentrated fermented milk as defined by Codex Alimentarius (“Codex standards for fermented milk,” 2003). According to this definition, milk is fermented when the protein content has been raised, before or after fermentation, to at least 5.6%. Concentrated fermented milks include traditional products such as Stragisto (strained yogurt), Labneh, Ymer and Ylette.
Greek yogurt has a specific composition and texture
The straining process involves removing the lactoserum or “whey”, which consists primarily of water and lactose, the sugar in milk. As a result, the yogurt acquires a thicker texture, because it is more concentrated than normal yogurt. As the lactose content is reduced, it becomes more digestible for those that have problems digesting lactose.
The label reveals all
Given the lack of a controlled denomination for Greek yogurt, market practices and names differ per country. So, depending on what country you are in, you can find different names, such as Greek yogurt, Greek-style yogurt and strained yogurt, and different compositions. Besides straining, using certain ingredients (starch, cream, thickeners, etc.) can also change the consistency of the yogurt.
Reading the label provides useful clarifications on the real nature of the yogurt: the list of ingredients allows you to see if the texture has been modified by the addition of ingredients or only by straining, and the nutritional composition will tell you whether the protein content exceeds 5.6 grams per 100 grams of yogurt (see the Codex definition – concentrated fermented milk).