My husband and I eat a LOT of yogurt in the house. If you look at our grocery cart every week, you’d think we had four kids at home, judging from the multitude of 5.3-ounce cups of Greek yogurt (enough to take as handy snacks almost every day of the week) and the larger 36-ounce tubs for snacking and lunch on our days off. I’ll even admit to a phase of buying 4-packs of those tiny Chobani Indulgences, which I’m pretty sure defeats the entire purpose of eating yogurt! The thickness, creaminess, and tartness of Greek-style yogurt make it the perfect foil for the sweetness of fruit, both dried and fresh, and the crunch of granola.
Given my fondness for the fermented dairy product, you’d think I’d have done some tinkering at home, but I’m ashamed to say that I’ve never given yogurt-making a whirl. Two recent NPR stories about yogurt bacterial culture and cultural differences in yogurt just might be the impetus I need to start tinkering in my own kitchen.
Yogurt is one of those foods that is much more than the sum of its parts. You can count on one hand what makes up its most elemental and traditional incarnation: You take (1) heated milk, add (2) bacteria and let it sit, so that the bacteria has the chance to feed on the milk’s lactose and produce lactic acid as a waste product. The elevated temperature of the milk allows the bacteria to work at maximum capacity, since they are thermophillic, or heat-loving. The heat also helps to denature, or unwind, the proteins, so that they can re-align themselves. This realignment is what transforms milk from a liquid into a creamy, semi-solid fermented dairy product. Commercial production of yogurt relies on only a few isolated strains of bacteria. Streptococcus thermophilus and Lactobacillus bulgaricus are the workhorses, while some other strains (e.g., Lactobacillus acidophilus, Bifidus regularis, and Lactobacillus casei) play more of a supporting role, providing probiotic benefits but not much in the way of flavor.
In contrast, traditional, non-commercial yogurt-making is much more fascinating. It’s a process that is in some ways reminiscent of making sourdough bread. In the artisanal bread world, it is not uncommon to hear about 160-year-old mother starters which are lovingly maintained and nourished in order to make generations upon generations of bread. Similarly, there are starter cultures of yogurt. As long as you continue to save a portion of the yogurt to use in fermenting your next batch of milk, you can keep the cycle going. If you try this technique at home using commercial yogurt as the starter culture, you may get a batch or two of yogurt, maybe even three, but after that, what you make will become a much more watered-down product. And who values that quality in a yogurt?
So then how are some yogurt starter cultures virtually immortal? In regions of the world where yogurt is still made daily by ordinary folks, as in Eastern Europe or India, heirloom starter cultures are the key to yogurt longevity. As cookbook author Sandor Kentz tells The Splendid Table, these heirloom starter cultures are “evolved communities of bacteria” that over time have been able to build a thorough defense against other bacteria in the environment, making them much more resilient. Some would also say that they can taste the difference. Take Veena Mehra, who emigrated from India in the 1970s and discovered that American store-bought yogurt just wasn’t as creamy or tangy as the yogurt of her native land. In order to recapture the taste of Indian yogurt, she packed away a bit of the yogurt (in her purse!) made by her family in Mumbai. Almost forty years later, she is still making yogurt with a descendant of that mother culture!
If you’re like me and interested in some yogurt experimentation, you can find all sorts of mother cultures, including Bulgarian, Finnish, and kosher varieties, here. Now go forth and multiply!