The discovery of Lactobacillus bulgaricus started with simple curiosity and a touch of homesickness. Shortly after microbiologist Stamen Grigorov got married, he left his home in Bulgaria to take a job as a research assistant at the Medical University of Geneva in Switzerland, where he had graduated medical school. He took along a clay pot of his new wife’s homemade Bulgarian yogurt.
Yogurt is a staple in Bulgaria, and it’s been that way for centuries. Women used to make their own yogurt at home, in clay pots like the one Mrs. Grigorov sent to Switzerland with her new husband. Today, people eat yogurt as a condiment, a soup base, a beverage, and a snack food. At the turn of the 20th century, some researchers were starting to make impressive claims about yogurt’s health benefits. That sparked Grigorov’s curiosity, and he smeared some yogurt on a microscope slide for a closer look.
Tragically, history doesn’t record how Grigorov’s wife responded to learning that he’d used her thoughtful gift as a science experiment. It’s difficult to even find a record of her name, despite the fact that her yogurt made history and changed a whole national industry.
The work took hours of staring into a microscope – since staring into microscopes was Grigorov’s actual job, he probably took it in stride – but in 1905, he identified the rod-shaped bacterium that turned milk into yogurt. Lactobacillus bulgaricus feasts on the lactose in milk, producing a specific set of fatty acids. The result is a thick, slightly tart substance that makes a tasty dip for your pita bread.
Fermented dairy foods like yogurt and cheese may have helped early farmers feed their children thousands of years ago. It’s easy to imagine the accidental discovery that a jar of goat milk had turned into something sort of lumpy and creamy, but ancient people quickly realized the value of the stuff and started fermenting milk into curds and yogurt on purpose. And it’s no coincidence that some of the world’s oldest evidence of fermented milk comes from places like Bulgaria, the Middle East, and central Asia. Those are the places where the climate is just right for L. bulgaricus to flourish and turn milk into yogurt. If you want to make yogurt anywhere else, you have to import bacterial cultures (which the Bulgarian government patented during the Cold War).
Most people outside southeastern Europe and the Middle East hadn’t even heard of yogurt in 1905, but Grigorov’s discovery helped change that. He found L. bulgaricus at around the same time that a slew of scientists published papers claiming that people who ate yogurt tended to live longer. Yogurt took western Europe by storm, and because Bulgarian yogurt, in particular, had scientific evidence behind it, it became the yogurt of choice for health enthusiasts in the 1920s.
But the yogurt for sale in Switzerland, where Grigorov made his discovery, wasn’t much like the pot of homemade yogurt he’d carried across Europe to his new lab. Most of the commercial yogurt producers used cow milk instead of the sheep’s milk that Bulgarian makers used. And while most households in Bulgaria had their own yogurt recipes and their own strains of L. bulgaricus, industrial production was vastly different.
“When scientists and manufacturers took over the process, they introduced strict measurements, specialist equipment, and ‘pure cultures’ that excluded any additional microflora found naturally in homemade yogurt,” wrote the BBC’s Madhvi Ramani in 2018, in a fascinating exploration of what happened to a traditional staple when it met the 20th century economy. History doesn’t record how Mrs. Grigorov felt about that, either.
Ironically, even as global popularity changed Bulgarian yogurt, it also turned the humble foodstuff into a symbol of Bulgaria’s national identity – which the country, newly subsumed into the Soviet Union, wanted to maintain. So in 1949, Bulgarian government sent microbiologists from house to house, sampling homemade yogurt and choosing the L. bulgaricus strains they liked best to create an official national yogurt. The Bulgarian government still owns the patent and export rights to that strain today. It’s surprisingly popular in Japan.