'Eternal' Yogurt Theoretically Lives Forever, Tastes Great

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Family heirlooms, those precious objects handed down from one generation to the next, can vary wildly in their value. Whereas an article of jewelry might fetch a handsome price at auction, other inheritances carry only sentimental value. One Indian-American immigrant mother’s gift to her daughter falls somewhere in between: a simple batch of plain yogurt, but one unmatched by any store-bought variety. According to NPR, this 40-year-old yogurt has been regenerated over decades, its taste preserved and passed down.

Though grocery store shelves  are stocked with enough varieties of yogurt to try a new type every day for weeks, the supply available in Oklahoma in 1970 wasn’t quite so diverse. As a new arrival from India, Veena Mehra was disappointed to discover that American yogurt was drastically different from the thick, rich, homemade variety she had taken for granted. A trip back home to Mumbai sometime around 1975 reminded her tastebuds exactly what they were missing out on, and Mehra resolved never to go without again. Before the days of strict TSA security checks, the solution was simple: she simply packed herself a portion of yogurt, placed it carefully in her purse, and flew back to American soil.

The fact that a container of yogurt survived a 21-hour flight un-refrigerated might have remained a fleeting curiosity—a souvenir from home quickly consumed and forgotten. That is, if not for one crucial property of yogurt: it is, in a sense, immortal. With a community of live bacteria—Streptococcus thermophilus and Lactobacillus bulgaricus, to be specific—constantly working to turn the lactose in milk into the lactic acid that gives yogurt its tang, Mehra’s one-time import could serve as a ‘starter’ for theoretically infinite batches of yogurt. The process she uses is simple, and requires only that she save as little as a spoonful of yogurt from a previous batch to make a new one. NPR got the inside scoop on how she does it:

She takes two cups of whole organic milk out of the fridge and lets it get to room temperature. Then she warms it over medium heat on the stove for 2.5 minutes. Next, she pours it into a plastic tub and adds a spoonful of yogurt from the old batch to the warm milk, mixing them together. Then she covers it with towels and puts it in the microwave (not to zap it, just to get it out of the way). The next morning, she's got her yogurt, and it goes back in the fridge.

According to microbiologist Rachel Dutton, Mehra’s unchanging method means that even four decades later, whatever’s sitting in her fridge now is probably a very near relation to the contents of the container she brought back so long ago, in terms of both taste and bacterial culture. That’s good news for all the Indian families she has shared it with over the years, not least her own. Her daughter admits to thinking that store-bought American yogurt “is really gross” in comparison, and her grandson is growing up with Mehra’s yogurt as a kitchen staple now, too, so the original bacteria is still going strong. Unfortunately, industrially produced yogurt won’t regenerate quite as reliably, so aspiring dairy DIYers will have to get their hands on a good heirloom starter to kick off their own never-ending yogurt supply. Maybe Veena Mehra will share a spoonful of hers.