Making yogurt isn’t cooking. Not really. It’s more like conjuring spirits: You create the conditions that summon mysterious creatures, invisible to the naked eye, to do all the real work.
In the case of yogurt, the “creatures” are good bacteria, or “live, active cultures” or, to use their trendier handle of late, probiotics. Whatever you call them, the lactic acid bacteria are the kitchen grunts, transforming milk into thick, tangy yogurt while you brag on social media about your experiments with heirloom cultures. The process, I guess, echoes the hierarchy of restaurants: the hidden, anonymous line cooks (the cultures) do all the heavy lifting, and the head chef (you) takes all the credit.
Making yogurt is easier than cooking, at least once you grasp its unique demands. When I decided to try my hand at it (and thumped my chest with a requisite Facebook post), I was somewhat surprised by the reaction: Four people immediately mentioned their own experiences — or their family’s experiences — producing yogurt at home. I had offers of assistance and/or a recipe.
The cynics among us might think this fascination with homemade yogurt is connected to our desire for prolonged life (or the fact that most supermarket brands are larded with stabilizers, sweeteners and other additives to mute the natural flavor and texture of fresh yogurt). After all, beneficial bacteria — like the kind in yogurt with live, active cultures — have been linked to improved digestion and to a reduced risk of heart disease. The cultures might even improve our mood.
In one study, a doctor noted in Psychology Today in 2012, “bacteria-fed mice had significantly lower levels of the stress hormone corticosterone and displayed significantly less behavior linked with stress, anxiety and depression than mice fed plain broth.”
Then again, the less cynical might view yogurt from a wider perspective. Even though the name “yogurt” has its roots in the Turkish language (the root word, “yog,” means to condense or intensify), the practice of fermenting milk is thought to be found in most cultures, stretching back thousands of years. Yogurt is practically a universal constant, like gravity or the speed of light, an easy method to preserve milk wherever animals produce it.
Perhaps due to its ubiquity, yogurt can be created in numerous ways, some requiring sophisticated equipment and others needing little more than what was available to the medieval Turk: milk, lactic acid bacteria and a simple container for the two ingredients to do their thing. These days, the basic process involves heating milk (whole, low-fat or nonfat are fine, although the lower the fat, the thinner the yogurt) to 180 degrees, cooling it to around 115 degrees, adding a starter to the warmed milk, pouring the cultured milk into jars and placing the jars in an incubator to ferment over several hours.
Within that broad outline, however, there are countless variations.
“Here’s the reality of yogurt,” says Sandor Ellix Katz, author of “The Art of Fermentation” (Chelsea Green, 2012). “There is no single magical universal recipe for how you do it.”
In making my own yogurt, I wanted to try a variety of approaches, both simple and elaborate. Yes, I was curious as to how different cultures and incubators would affect flavor and texture, but I also wanted to avoid a single, high-tech technique that would unnecessarily complicate a fermenting process that Middle Eastern grandmothers have mastered for centuries without the benefit of digital thermometers, electric yogurt makers and heirloom starters.
Let’s get one thing out of the way first: No matter what a recipe calls for, you don’t need to sterilize your jars, lids, spoons, saucepans, pitchers or other tools by boiling them in water. As Katz, pointed out, the process won’t achieve much in an environment without an air filtration system. “Household sterilization is a little bit of a myth,” he says. Thirty seconds after you place a so-called sterilized jar on a drying rack, “it’s not sterile anymore.”
You can, instead, just wash your equipment with soap and hot water. That will shave valuable minutes off the yogurt-making process.
My first attempt at yogurt was something of a disaster, the result of sheer hubris. As I waited for the heated whole milk to drop into the necessary fermentation zone — between 104 and 120 degrees Fahrenheit, depending on your information source — I thought I could outsmart the process. Because I was using semi-cold Brown Cow yogurt as my starter, I decided I should add it before the milk reached the target range, lest the culture cool the liquid to an undesirable temperature. There was just one problem with my logic: High heat will kill your live, active cultures. My first batch was a watery mess, closer to sour milk than yogurt.
I learned another lesson from that first test: Don’t waste time by letting the heated milk cool on its own. Without assistance, the milk takes forever to drop to 115 degrees. (Okay, maybe an hour, but it feels longer.) Just place the saucepan in a sink filled with a few inches of ice water; the milk will cool in minutes, not millennia.
As part of the process to attain yogurt sensei status, I worked with three types of incubators to determine whether any one would outperform the others (opting not to try food chemistry guru Harold McGee’s preferred approach of wrapping jars in kitchen towels). I tried a Thermos, a basic insulated cooler and a yogurt maker that I bought online for $50 at Cultures for Health. In general, the incubator’s job is to hold milk at the proper temperature so the starter can convert the lactose into lactic acid, which in turn helps coagulate the proteins and fat globules into the semi-solid mass that we know as yogurt.
The key, then, is an incubator that maintains the ideal temperature long enough for the milk to set. Katz says that at 115 degrees, it takes about three hours to set the milk. Problems, he adds, can arise when the cultures continue to ferment too long at that temperature; they can begin to curdle into something far too solid. He prefers to ferment his jarred milk in a small insulated cooler filled with warm water, around 110 degrees, and let the jars sit for between four and eight hours. The longer fermentation also allows the cultures to develop more tang.
Among the three incubators, the yogurt maker held its temperature the best, as you might expect from a machine with a heating element. The Euro Cuisine unit doesn’t have an external thermometer, but I tested a jar of tap water in the machine and learned that the contraption maintains a steady 112-degree temperature. As such, the unit immediately produced a far firmer yogurt than the stuff I pulled from the Thermos or cooler, which initially turned out thinner versions until I learned how to better control temperature and gauge how long the jars should ferment.
But should you not want to shell out for such a machine, you can still produce thicker yogurt with a simple trick that Katz taught me: After initially heating the milk to 180 degrees, you can continue cooking the liquid at that temperature for 15 minutes while stirring frequently. The prolonged heat treatment helps to further evaporate and concentrate the milk, resulting in a firmer final product.
The other important variable here is the starter. As mentioned earlier, I initially used Brown Cow yogurt as a starter: a quarter-cup of the stuff to ferment a quart of whole milk (based on a recipe in Jennifer McGruther’s “The Nourished Kitchen,” Ten Speed Press, 2014). Brown Cow includes both L. bulgaricus and S. thermophilus, the cultures required by law for real yogurt, and also features two other probiotic cultures to promote health. When I incorporated the starter into the warm milk and sealed the cultured liquid into a Thermos for 12 hours, it produced a lovely, creamy yogurt with a mild tartness. It did require straining to achieve a thick, Greek-style texture, although it never reached the consistency of commercial Greek yogurts with added thickeners, which have a preternatural bounce.
I also bought Greek and Bulgarian heirloom starters, each of which sells for $12.99 for two packets at Cultures for Health. “Heirloom cultures are the variety our great-grandmothers would have used. They function similarly to traditional sourdough: A small amount from each batch is used to make the next batch, and they are passed from person to person,” e-mailed Julie Feickert, owner of Cultures for Health.
“The exact origins as well as specific bacteria strains of any heirloom starter can be a bit murky as, by their nature, they are passed down from person to person over hundreds or even thousands of years,” Feickert added. “It is our understanding that those cultures did originate from those regions, but in the end there is not [a] solid way to independently verify that.”
As promised, the milk infused with the Greek starter, when incubated in the yogurt maker for 12 hours, produced thick and tangy results — tangy enough to induce that tingling fish-gill reaction around the throat. The Bulgarian culture was milder but just as creamy when left in the yogurt maker for 13 hours. (I also heated the milk an extra 15 minutes with both, as Katz advised.) No straining was required for either, their texture already thick and decadent. Even though I prefer tartness, I found myself magnetically attracted to the more muted tang of the Bulgarian yogurt.
So for my latest one-quart batch, I used a tablespoon of the leftover Bulgarian yogurt as a starter. The reduced amount is a technique I also nicked from Katz, who discovered that using less starter translates into a thicker yogurt. Sure enough, the results were startling: The yogurt was rich and firm when I removed the jars from the Euro Cuisine unit, the texture like that of silken tofu.
Theoretically, this Bulgarian yogurt culture could outlive me, its flavors evolving over the years as it potentially picks up bacteria native to my environment. I just have to treat it right and feed it fresh, warmed milk every week or so. Then this mysterious, living thing in my refrigerator will continue to toil without complaint, as I accept all the applause for its deliciousness.
Sandor Ellix Katz will join today’s Free Range chat at live.washingtonpost.
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