Published May 1, 2011. From Cook's Illustrated.
If all Greek yogurt starts with the same basic ingredients—milk and cultures—what makes some brands thick, rich, and creamy while others are watery and sour?
You wouldn’t know from the recent surge in Greek yogurt sales that Americans have never cared much for the tangy plainness of yogurt. In recent months, sales of the Greek variety have jumped 160 percent compared with a mere 3 percent hike for regular yogurt—and for good reason. Like much of the yogurt traditionally made across Europe and the Middle East, Greek yogurt is considerably thicker, richer, and creamier than the American stuff. Even the low-fat and nonfat versions taste remarkably decadent. Greek yogurt is good eaten plain, swirled with honey or jam, or sprinkled with nuts, and in the test kitchen we prefer it to thinner, runnier American yogurt in creamy dips and sauces.
But nowhere is the trend toward Greek yogurt more obvious than in grocery stores. Where once only one or two brands were available, supermarkets now carry nearly a dozen national brands with a variety of fat levels. Even longtime producers of regular yogurt have entered the game, launching their own lines of Greek-style yogurt to keep from getting pushed out of the market.
Being fans of the Greek stuff ourselves, we weren’t surprised by the impressive sales figures. But we did wonder if all of these new brands measured up to the hype. To find out, we rounded up 10 nonfat plain Greek yogurts (nonfat is the most widely available variety). As soon as we pulled back their foil seals, we noticed clear differences. Some yogurts stood up in stiff peaks, while others were loose and glossy, even a little watery. Those discrepancies became even more apparent once we started eating. Flavors ranged from utterly bland to lightly tangy to strongly sour. A few samples boasted a rich, luxurious consistency, while others revealed their nonfat status all too obviously. Our least favorite sample was grainy and curdled and reminded tasters of cottage cheese.
When the scores were tallied, we found three brands that almost nobody liked, six that ranged from barely acceptable to very pleasing, and one that we all loved. Now we just needed to know why.
Clearing the Whey
First, some background information about the yogurt-making process. Like ordinary yogurt, the Greek style is made by adding two active bacterial cultures—S. thermophilus (St) and L. bulgaricus (Lb)—to milk. During fermentation, these cultures digest the milk’s sugar (lactose) and produce the lactic acid that makes yogurt thick and tangy. The major difference between the two types is that true Greek yogurt is strained to remove most of its liquid whey. The result is not only thicker than American-style yogurt, but also considerably higher in protein. In fact, it can take up to four times as much milk to make Greek yogurt using the straining process as it does to make ordinary yogurt. This high-protein product is also lower in carbohydrates and salt and usually less acidic, since much of the lactic acid (along with the carbs and salt) drains out with the whey.
But as we discovered, some manufacturers are getting at this thicker, creamier product in other ways. Rather than draining the whey with an expensive mechanical separator, they skip the straining process altogether and fortify the yogurt with thickeners like milk protein concentrate, pectin, or gelatin. Adding milk protein concentrate boosts the percentage of milk solids, buffering acidity; pectin and gelatin gel the more fluid yogurt so that it mimics the thickness of a strained product. Whichever additive is used, fortification is faster and cheaper—but not surprisingly, it produces an inferior product. The two yogurts that we liked the least were fortified and had considerably higher levels of carbohydrates than most other brands—a pretty good indication (although neither company would confirm it) that those manufacturers are not straining out the whey. Tasters found both samples sour to the point of almost tasting spoiled and their textures equally unpleasant. To many, one gelatin-thickened yogurt resembled pudding. Another yogurt, which includes pectin and inulin (a flavorless dietary fiber that absorbs liquid) and contains less than half the protein of other brands, was not only “watery” and “broken,” but also “curdled.”
A Matter of Culture
Fortification is one factor that likely sank two brands to the bottom of the rankings. Another equally important variable that determines yogurt flavor and texture is the specific cocktail of bacterial cultures. According to Dr. Mirjana Curic-Bawden, a senior scientist for Chr. Hansen, a leading international supplier of food cultures, all yogurts must contain St and Lb, but exactly which strains of those cultures are added will affect how tangy, rich, or smooth the yogurt will be. The tricky part for manufacturers, Curic-Bawden said, is getting the combination just right. Manufacturers that select a bacteria cocktail prone to heavy acidification might produce a harsh, sour yogurt even if they strain out a good bit of the acidic whey. Similarly, employing a mix of mild cultures (and adding milk proteins) will help compensate for the acidity of unstrained yogurt, although, as we seemed to find with one product, it won’t necessarily be a perfect solution.
As with any finicky recipe, matching up the right ingredients with the right method (some manufacturers have their own patented approach to straining) makes all the difference. To us, most of the yogurts we sampled didn’t hit the mark perfectly. In fact, we found only one that we’d enthusiastically seek out, and it wasn’t made by one of the better-known producers of Greek yogurt. Our favorite, a strained product made by a market newcomer, boasted just the right combination of thick, unctuous creaminess and mellow tang. This brand was also the winner and runner-up, respectively, of our full-fat and low-fat tastings, and it happens to be the only brand imported from Greece. In fact, this is one yogurt that we’re happy to eat with—or without—a spoonful of honey.
Cooking with Greek Yogurt
After discovering that we have very particular tastes when it comes to eating Greek yogurt plain, we wondered if we’d pick up on those differences when the yogurt was used as a cooking ingredient in tzatziki sauce (a Greek condiment) and our Light New York Cheesecake. It turns out that the other ingredients in the sauce (garlic, mint, and cucumbers) didn’t blur the differences among the brands much at all; in fact, the tzatziki scores almost exactly matched the scores we gave these yogurts in the plain tasting: The top-ranked yogurts made thick, creamy, well-balanced sauce, while sauces made with bottom-ranked brands were “runny” and “sour.”
But the baked application was more forgiving. Here, a bottom-ranked yogurt was acceptable—even preferred by several tasters, who appreciated the extra moisture and stronger tanginess that it brought to this dense, rich dessert. The bottom line? We’ll stick with our favorite, but in a pinch, we won’t worry about the brand if we’re baking.