To find out, we set up an Olympics of yogurt. We zeroed in on plain yogurt because it’s good for cooking and because we knew that added flavors would distract from differences in taste or texture. We also excluded nonfat yogurts, reasoning that it would be unfair to compare them to products with higher fat contents. Although we found lots of international options, we included only products that were available nationally at major supermarkets. Our final lineup consisted of eight low-fat and American yogurts: three Icelandic; two Bulgarian; one Australian (or “Aussie,” the company’s preferred term); our favorite whole Greek yogurt, Fage Total Classic; and our favorite traditional American yogurt, Brown Cow Cream Top. Tasters sampled them plain, with granola, and in tzatziki, a Mediterranean sauce flavored with cucumber, garlic, and mint.

Prior to our research, we had assumed that the international yogurts we saw on supermarket shelves were imported from the countries on their labels and had just recently become available in the United States. But, surprisingly, we were wrong. Every yogurt in our lineup was made in America. When we talked to the companies, we heard a common refrain: The founders loved the yogurt they ate as kids or while on vacation. They couldn’t find it in America, so they decided to make it themselves. There was one outlier: Vermont-based Green Mountain Creamery was already making a Greek yogurt when it added skyr to its line.

Another surprise: In the United States, there are no special requirements for each of the styles. The U.S. Food and Drug Administration (FDA), which regulates yogurt, defines yogurt as milk or cream that has been cultured with two species of bacteria, Streptococcus thermophilus and Lactobacillus bulgaricus. It also sets certain requirements for elements such as milk fat, acidity, and sweeteners. But on the subject of how one style of yogurt compares with another, the FDA hasn’t ruled.

Even without the clarification of FDA regulations, referring to a yogurt as Bulgarian, Icelandic, or Australian does indicate distinct differences. The yogurts we tasted varied wildly in flavor and texture. Some reminded us of yogurts we already knew and loved. Others really surprised us. 

Icelandic skyr (“skeer”) was the most like Greek yogurt. Traditionally, both styles are strained and have dense textures. The ones we tasted were “lush” and “decadent,” so thick we could stand a spoon in them. The skyr products were generally more tart and tangy than sweet. One in particular was “bright” and even “lemony.”

The Bulgarian yogurts were totally different. They were by far the thinnest products in our lineup; their runnier texture was unexpected, but some of us loved the way it softened the crunchy granola. And because we strained them before making tzatziki (an optional step common when using thinner yogurts in recipes), the finished sauces had the pleasantly thick, creamy, pillowy texture we wanted. The Bulgarian yogurts were bracingly tart. In addition, tasters noticed “funky,” “salty,” almost “savory” qualities that were too strong for some when eating the yogurts plain but worked well in tzatziki alongside other bold ingredients.

In terms of texture, the Aussie and traditional American yogurts fell squarely in between the other two styles. They were “very smooth” and “creamy,” looser than the Icelandic and Greek products but thicker than the Bulgarian ones. In all three blind tastings, the Aussie and American yogurts tasted “mild” and “slightly sweet.”

Ingredient-wise, yogurt is simple. It’s just milk and/or cream and bacterial cultures. One product we tasted also contained a thickener (pectin), but otherwise that was it—despite the dramatic differences we saw in our tastings. To understand why the yogurts varied so much, we knew we had to learn more about how yogurt is made.

Traditionally, milk was cooked slowly until some of its moisture evaporated and it thickened slightly. Today, manufacturers can achieve that thick consistency in different ways. Robert Roberts, a professor of food science at Pennsylvania State University, told us that it’s common to use evaporated milk instead of regular milk because it’s thicker and, without the extra water weight, cheaper to transport. Producers can also make their starting milk thicker by amping up the amount of milk solids, generally by adding nonfat milk powder. Because these products are technically milk without any other ingredients added, they don’t have to be listed differently on labels. All the manufacturers of the yogurts we tasted were reluctant to share details on their milk bases.

Using evaporated milk or nonfat milk powder also allows manufacturers to adjust the yogurt’s fat content. The yogurts in our lineup contained 8 to 11 grams of fat per serving with the exception of the one low-fat product, a skyr, which had 3.5 grams per serving. But even the low-fat yogurt tasted plenty rich. Other variables in processing and style were more important in determining the final product.

To begin the fermentation process, the milk is heated and cultures are added. The cultures convert the lactose (the sugar naturally present in milk) to lactic acid, which gives yogurt its characteristic tang and causes the proteins in the milk to gel, or thicken. The products each contained a variety of cultures, and we were curious about how they differed.

First we looked at the cultures required by the FDA, Streptococcus thermophilus and Lactobacillus bulgaricus. These two species of bacteria have countless different strains. To learn more about them, we turned to Mirjana Curic-Bawden, a scientist at Chr. Hansen, a company that develops cultures for use in yogurt and other dairy products. She explained that all the strains “have different characteristics with regards to texture, flavor, mildness, [and] how much acid they can produce.” In other words, manufacturers select the specific strains that will create the flavor and texture they want. Some cultures are specifically designed to have more acidity. Other cultures will stop converting lactose to lactic acid at a certain point, so the yogurt can have a long shelf life and won’t become unbearably tart. Although each species appears only once on a given label, it’s possible that companies are using more than one strain of each.

One of the skyrs we tasted includes an interesting detail on its packaging: The Streptococcus thermophilus is described as an “heirloom skyr culture.” The manufacturer told us that an Icelandic dairy got the cultures in the 1920s and that they’re likely hundreds of years old. It’s a good marketing story, but there’s nothing new about isolating specific strains and keeping them for decades—Icelandic women did it centuries ago to make skyr. Today, large companies isolate cultures because they develop certain desirable flavors and textures in yogurt. Doing so also ensures consistency. As Curic-Bawden explained, “from the point of yogurt making/functionality, the culture is still doing what other yogurt cultures used in skyr and Greek [yogurt] do,” regardless of whether they’re identified as heirloom or not. In other words, though those heirloom cultures are vital to developing that skyr’s specific flavor and texture, they’re no more unique or special than any other yogurt’s specific blend of proprietary cultures.

What about the other species of cultures listed on our yogurt’s labels, such as Lactobacillus paracasei and Bifidobacterium lactis? The industry experts explained that they were secondary in importance to Streptococcus thermophilus and Lactobacillus bulgaricus. As Roberts said, they “really don’t participate a great deal in the fermentation.” He theorized that extra cultures are added “because they connote probiotics,” but—and he emphasized this—the information on the labels is often vague and doesn’t tie the cultures to specific health benefits. Because they’re more costly, cultures with bona fide health benefits would be specified (usually with a bulky alphanumeric code) on a product’s label.

After the cultures are added, the yogurts ferment. About half the companies shared information about their fermentation processes. Among those, we saw an enormous range—from just 4 hours to a two-part fermentation process totaling 30 hours. That means that some cultures had significantly more time to grow and develop flavor. It also gives the cultures more time to convert lactose, the sugar naturally present in the milk, to tangy lactic acid. Sure enough, the yogurts with the longest fermentation times in our lineup tasted the tartest and had some of the lowest sugar contents, about 5 and 6 grams per serving.

To get a fuller look at the differences, we had an independent lab measure the yogurts’ pH levels (a measure of tartness). All the products in our lineup were fairly acidic. Most measured between 4.11 and 4.4. Two of the yogurts had very low pH levels, just 3.61 and 3.77. It’s no wonder they were so bracing

After the yogurts are cultured, some are ready for packaging. Two of the thicker styles in our lineup, Greek and Icelandic, are strained before being packaged. Historically, yogurt makers in Greece and Iceland strained their yogurts using cheesecloth. Now manufacturers can spin out the whey using a centrifuge or drain it using a special filter. Removing the whey (which is mostly water) concentrates the protein in the yogurt, which explains the sizable differences in overall protein we saw on nutrition labels. The Greek yogurt contained 20 grams of protein per serving. The Icelandic skyrs had 24 to 26 grams, suggesting that they had been strained even more. The Bulgarian, Australian, and traditional American yogurts contained much less protein, 8 to 12 grams per serving.

Straining also affects the overall sugar content. Lactose (the natural sugar in milk) is mostly stored in the whey, so when the whey is drained, the sugar goes with it. As a result, the Greek and Icelandic strained yogurts had 3 to 9 grams of sugar per serving, while the unstrained Aussie and traditional American yogurts had 10 and 13 grams, respectively.

The takeaway from this testing is that yogurt preferences are dependent on the style. The Icelandic-style skyrs we tasted were just as thick and luxuriously dense as our favorite Greek yogurt. Their mild-to-tangy flavor was similar to that of Greek-style yogurt, too. If you like Greek yogurt, give these a try. The Bulgarian yogurts were dramatically different. They’re best for those who prefer thinner yogurt with a funkier, tangier flavor. That acidity boosted the flavor of the tzatziki and would add vibrance to other savory dishes. The Aussie yogurt was the most similar to what most Americans ate before Greek yogurt came onto the scene. It was fairly sweet and, while thinner than the strained yogurts, still thick and rich. Because they’re not strained during processing, the Bulgarian, Australian, and traditional American yogurts can’t be used as a direct replacement for Greek yogurt in recipes. There’s an easy fix, though. They can be strained overnight in a fine-mesh strainer lined with a coffee filter or cheesecloth. The yogurts we tasted vary so much in both flavor and texture that we think they’re all worth a try. That’s why we’ve opted to list them by style and then by texture, from thickest to thinnest, instead of ranking them in order of preference. These international yogurts were plain, but they were anything but boring.