A recent batch of Veena Mehra’s yogurt in Houston. She’s been making yogurt the same way, with the same starter, for about 40 years. PHOTO: Nishta Mehra

If you’re making your own yogurt at home, you need an old batch to make a new batch. And the community of microbes in that yogurt starter — and the flavor — should remain relatively unchanged if you make it the same way every time. That’s what Rachel Dutton, an assistant professor of microbiology at the University of California, San Diego who studies cheese and other dairy products, says, anyway.

In many countries, like India, most yogurt is still made daily, even twice a day, at home. And that homemade yogurt tends to have a different flavor and texture — thicker and more sour — than the stuff made in a big yogurt factory.

Veena Mehra, who emigrated to the U.S. from India, discovered when she first arrived in Oklahoma in 1970 that American yogurt wasn’t like what she was used to eating back home.

“It just did not taste the same,” she tells me. Her husband was studying at the University of Oklahoma, and there weren’t any Indian groceries in Norman. “I tried buttermilk, and then I tried to use the yogurt I found at the store to make my own, but it just didn’t work.”

She continued to long for her homemade yogurt, so in 1975 or 1976 (she can’t remember exactly what year it was), when she returned to Mumbai to visit her family, she decided to bring some yogurt starter back with her on the plane.

Cooling cucumber raita made with yogurt is a common accompaniment to spicy Indian dishes. PHOTO: Magda Wojtyra/Flickr

“I just put it in a container and then in my purse,” she says. The yogurt survived the 21-hour journey to Memphis, Tenn., where they’d moved. Two days later, she was making yogurt again. And, most important, she says, “It tasted good: tart and thick.”

Some 40 years later, Mehra, now 68, has kept that same starter going. She says she shared it with other Indian families in Memphis, and brought it with her when she moved to Houston three years ago after her husband died, to be closer to her daughter, Nishta, and grandson.

Read more on the science involved in the making of yogurt and how you can make your stash last longer here, courtesy NPR’s Salt.