Everything You Ever Wanted to Know About Yogurt

One of the world’s most recognizable dairy products, yogurt is a living, versatile symbol of human innovation

Yogurt is one of the world’s most recognizable dairy products, but how often do we think about where it comes from, much less appreciate it as a living symbol of human innovation that has spawned an entire world of flavors, textures, and regional preparations? The answer: not nearly enough. That said, exploring the world of yogurt can be simultaneously exciting and a lot to tackle. So without further ado, let’s dive in.

What is yogurt?

On a basic level, yogurt is a dairy (or, nowadays, even plant-based) product made through the process of fermentation. By combining heat, certain naturally occurring bacteria, and (often) thickeners, producers can create a variety of yogurts that vary in texture and flavor.

The sheer variety of yogurt can sometimes make visits to the dairy aisle overwhelming: There are regional styles, sweetened stuff made with natural or artificial flavorings, drinkable yogurts, plant-based yogurts, and on and on. Choosing between them all is more than just a personal preference; it often requires reading labels and trying different brands until you land on one that suits your taste. In other words, shopping for yogurt can feel like too much of a good thing if you’re not sure what to look for.

Who discovered yogurt?

“I don’t think you can point to an origin of yogurt,” says Charles Perry, an author of books on medieval Arabic cuisine and the president of the Culinary Historians of Southern California. “[Yogurt] developed spontaneously, probably everywhere that people consumed milk, or where [adults] had evolved the ability to metabolize milk.”

One widely accepted theory is that yogurt dates back several millennia to Mesopotamia. Archeologists have found traces of it dating to the Neolithic period between 10000 and 5000 BCE, but it’s more likely that it originated closer to 5000 BCE, around the time milk-producing animals were first domesticated. However, early traces of animal milking in parts of the world like Africa and the Middle East date to around 8500 BCE. Therefore, we can estimate that yogurt’s discovery occurred sometime within these three and a half millennia.

The actual discovery of yogurt is believed to be a complete accident. A popular theory is that herdsmen in the Middle East would travel long distances with dairy milk stored in bags made from animal stomachs. In the process, the combination of heat and the bag’s intestinal enzymes would cause the milk to curdle, resulting in yogurt. Eventually, this method was deemed the safest way to preserve dairy milk for longer periods, and humanity’s love of yogurt was born.

The disagreement around the exact origin of yogurt is arguably exacerbated by language: Various cultures have long had their own words for sour milk. “Thirteenth-century [Arabic] cookbooks distinguish between laban haleeb (freshly milked laban) and laban haamid (sour laban),” says Perry. “In modern Syrian Arabic, laban always means yogurt, and fresh milk is haleeb. Ancient Greek had a word meaning sour milk, oxygala, but I don’t find evidence of any culinary use of it. Modern Greek, of course, uses the Turkish word.”

The Turkish word is “yoğurmak.” Commonly believed to be the origin of the word “yogurt,” it means to thicken, curdle, or coagulate. Some of the earliest references to it date back to 11th-century Turkey, where it was mentioned in contemporary texts. The Turks were also the first to evaluate yogurt’s medicinal use for a variety of illnesses and symptoms, such as diarrhea and cramps, and to alleviate the discomfort of sunburned skin.

The 13th-century Mongolian emperor Genghis Khan is purported to have fed his army yogurt, believing that it could boost strength and bravery. And in India, Ayurvedic scripts mention yogurt as far back as 6000 BCE.

“Ancient Indian scriptures, known as the Vedas, hint towards the existence of dairy and dairy products aplenty,” says Sonal Ved, a Mumbai-based writer and cookbook author. “Ayurveda too puts ‘dairy’ in a special food category. One of the depictions of the Hindu god Krishna, even today, can be seen eating mounds of makhan, which is essentially white butter churned from milk.”

Ancient as yogurt may be, its potential as a nutritional food wasn’t thoroughly explored until 1905, when a Bulgarian medical student named Stamen Grigorov discovered Lactobacillus bulgaricus, a strain of bacillus bacteria that causes the fermentation of yogurt, producing lactic acid. Grigorov’s discovery (he also studied the health benefits of lactic acid) spurred and backed up other studies that promoted yogurt — which wasn’t very well-known in the early 20th century — as a health food.

Today, it’s a grocery store staple almost everywhere, something that is widely credited to the combined efforts of Isaac Carasso and his son, Daniel. The elder Carasso was a Greek-Spanish businessman who in 1919 founded a Barcelona yogurt factory called Danone. Carasso went on to industrialize yogurt production, and in the late 1920s, his son expanded the company to the U.S. Eventually, Danone (known in the U.S. as Dannon) became Group Danone, a multinational food corporation. More recently, other major yogurt producers, including Yoplait and Chobani, have further broadened the market, exporting their products worldwide.

How is yogurt made?

On an industrial scale, yogurt production begins with raw milk transported from dairy farms to a processing plant for standardization, pasteurization, and homogenization.

Standardization refers to the process of separating raw milk’s fat, protein, and solid particles (i.e., lactose and minerals) before reincorporating them in specific quantities. This is how we get dairy products with varying levels of fat.

Once the milk has been standardized, it undergoes pasteurization, a process that kills harmful bacteria that could potentially be present in raw dairy milk. It also denatures the milk’s whey proteins, allowing for a more stable gel to form in the process.

After pasteurization, the milk is homogenized, which involves processing it under high pressure to break down the fat globules and create a more uniform texture. Any sweeteners or stabilizers are added to the pasteurized mixture prior to homogenization.

The processed milk can now safely be made into yogurt, but it must first rapidly cool. As it cools, living fermentation cultures are introduced to create the creamy and tangy product we’re looking for. The cultures typically include strains like Lactobacillus bulgaricus and Streptococcus thermophilus. These bacteria convert the milk’s natural sugar, known as lactose, into lactic acid, causing the dairy to coagulate and form yogurt’s signature sour taste.

The inoculated milk then enters the incubation phase, which lasts four to seven hours. The longer the mixture incubates, the tangier the final product will be. Maintaining proper temperature is critical in this step, since the bacteria will die if it’s too hot or too cold. Once the inoculated milk achieves a pH of 4.6, the mixture will solidify to form yogurt. Afterward, the yogurt is cooled to about 45 degrees, and transformed into a range of products that vary in texture, presentation, and flavor from additional mix-ins, like fruit.

How many kinds of yogurt are there?

Some might hear “dairy” and immediately assume cow’s milk, but goat’s and sheep’s milk are also commonly used to make yogurt, lending it their own nuances in flavor and texture.

“Sheep’s yogurt tastes very much like cow’s milk, but with a bit more brightness to it,” says Liam Callahan, co-owner and co-founder of Bellwether Farms in Sonoma County, California. Opened in 1990, the creamery specialized in sheep’s yogurt and cheeses before expanding into cow’s milk five years ago. “People think sheep’s milk is going to taste like goat’s milk, and that’s not the case at all,” Callahan says. “It has a higher level of minerals and fat, with 30 to 50 percent higher solids than cow’s milk, whereas goat’s milk has fewer solids than cow’s milk.”

Other than their differing milk bases, yogurt products can also vary according to regional preparation. Greek yogurt, for instance, is typically categorized as a thicker, creamier, and tangier yogurt, similar to labneh, a strained yogurt popular across the Middle East. “Traditionally, it’s a strained yogurt with an increased level of protein from filtering the milk and removing water,” Callahan says of Greek yogurt. The style has “done amazingly well” with consumers, he adds.

Then there’s Bulgarian yogurt, an unstrained yogurt found on many store shelves. Besides requiring Lactobacillus bulgaricus — the same namesake strain discovered by Stamen Grigorov — on its ingredient list, Bulgarian yogurt is formed by pouring warm, incubated milk into containers without further stirring or straining. The final result is creamy but not as thick as its Greek counterpart and has higher calcium and whey protein levels per serving.

The list doesn’t end there. Today you can also commonly find yogurt variations like kefir, a drinkable yogurt originally from the Caucasus region, and Icelandic skyr, which is strained, made with Icelandic heirloom cultures, and contains more protein than standard American brands. And there’s Indian dahi, which can be found in both American and Southeast Asian grocery stores.

“In India, predominantly, we use dahi,” says Ved. “It is made by adding culture to warm milk that forms a panna cotta-like goop, then whisked and used in various dishes.” Typically made with cow’s milk, dahi is tart, faintly sweet, and not as thick as Greek yogurt.

Today’s growing demand for plant-based options has created a market for vegan yogurts. Major brands and smaller plant-based producers are making them from coconut, oats, cashews, almonds, and soy. Just like dairy yogurt, they have their own unique characteristics. Depending on their base, vegan yogurts can include beneficial traces of calcium and protein, as well as healthy probiotic bacteria.

What does yogurt taste like?

A yogurt’s flavor typically comes down to several factors including milk type, preparation, and the use of additives. For example, strained yogurt tends to have a tangier flavor than unstrained yogurt since much of its whey and natural sugars have been filtered out. Some yogurt producers will also add sugar and other sweeteners to balance or dilute its natural tang.

The flavor of yogurt is also affected by the kind of milk used to make it, particularly the milk’s fat content. “The fat in our milk does fluctuate throughout the year as the animals change in their stages of lactation and what feed they’re getting,” says Callahan. “Cream and nonfat milk can also be blended together, and that’s technically ‘whole milk’ based on the standard of identity. [Producers] can even combine fat from different animals, but it would have to be specified in the ingredient list.”

The bacterial strains used in a yogurt recipe will also influence the taste. “There are a myriad of yogurt starters in the world, probably in some cases including other bacteria that don’t sour the milk but affect the flavor in some other way,” Perry says.

How do you cook with yogurt?

Aside from eating yogurt the obvious way — i.e. by the spoonful — you can also drink it as a probiotic beverage and use it in all sorts of ways.

“I think one of the best ways to use yogurt is as a marinade,” adds Callahan. “It’s an amazing flavor transporter that you can season any way you like. Its acidity tenderizes chicken, lamb, or beef, similar to using vinegar.”

“In the part of India where I come from, Gujarat, yogurt is a very important ingredient in cooking,” says Ved. “It’s the base of the popular Gujarati kadhi, it’s inside the dough to make theplas, it’s added to vegetable gravies, and so on.”

You can also use yogurt as a substitute for creamy condiments like mayonnaise, as the basis for all kinds of dips, fold it into recipes for additional protein and moisture, turn it into a frozen dessert, or add it to salad dressing and soups. When it comes to yogurt, there’s no shortage of wiggle room for experimentation.

How do I make yogurt at home?

Definitely. For the most part, DIY yogurt follows the same process as industrialized yogurt production, but with fewer steps. All you need is store-bought pasteurized milk, yogurt with live, active cultures (as a starter), a heavy pot, and a probe thermometer to monitor temperatures closely. There are plenty of recipes online that detail temperatures and waiting periods, as well as varying add-in ingredients like heavy cream and sweeteners, but these are the essentials.

“I warm milk and add a teaspoon of [the active] culture that has been carried forward from the years in my house,” Ved says of the overnight process she uses to make yogurt. “Thanks to the tropical Indian weather, it’s ready by morning. It’s usually an evening ritual.”

It’s not uncommon to see active cultures passed down in a household from one generation to the next. “When I was working in a newsroom a few years ago, I heard of this amazing story of a family in Mumbai that has something called heirloom curd culture,” says Ved. “It’s the same culture that has been going on in the family for several generations! I found that to be quite fascinating.”

Similarly, some immigrant families have gone to great lengths to bring their yogurt starters along to their new homes. “Lebanese immigrants to the U.S. would soak a clean handkerchief in yogurt and dry it out so they would be able to start their favorite yogurt in this country,” says Perry. “In many cases, they would bring more than one starter, with a number of families having starters that produced a mild, almost sweet yogurt only made for a week or two in springtime or fall.”

Making vegan yogurt entails different processes and waiting periods depending on which base is used. Since dairy yogurt cannot be used as a starter, probiotic capsules are substituted to kickstart the fermentation process.

How do you store yogurt?

In Europe, yogurt products are often left out at room temperature. But this isn’t the case (and isn’t recommended) for dairy products made in North America. The discrepancy comes down to how milk is pasteurized in the U.S. and Canada versus in the European Union; in the latter, UHT pasteurization allows milk products to remain safe for consumption at room temperature for up to three months. So if you find yourself in North America, keep your yogurt refrigerated.

What are some good recipes that use yogurt?

Dassana Amit’s Chaach (Indian Spiced Buttermilk)

Martha Rose Shulman’s Bulgarian Cucumber Soup With Walnuts

Madhur Jaffrey’s Mango Lassi

Alison Roman’s Spiced Marinated Lamb Chops With Garlicky Yogurt

Yumna Jawad’s Yogurt Flatbread

Yotam Ottolenghi’s Labneh with Olives, Pistachios, and Oregano

Ina Garten’s Lemon Yogurt Cake

Jamie Oliver’s Frozen Yogurts

Lidey Heuck’s Grilled Chicken With Yogurt Marinade

Natasha Kravchuk’s Tzatziki Sauce

Sylvio Martins is a freelance writer and actor based in Los Angeles.
Sophia Pappas is a Pittsburgh-based illustrator.

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