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.
Making yogurt is easier than cooking, at least once you grasp its unique demands. 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.
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. 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. Just place the saucepan in a sink filled with a few inches of ice water; the milk will cool in minutes, not an hour.
The incubator
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 starter
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 new book, “The Nourished Kitchen”). 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 1/8a3/8 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.
Nothing-plain-about-it Bulgarian yogurt
1quart whole, low-fat or nonfat milk
1packet (.04 ounces) Bulgarian yogurt starter (may substitute 1 tablespoon room-temperature cultured yogurt)
You will need an insulated container or yogurt maker to incubate the cultured milk; the directions below include information for each. You can use a cooler or a Thermos, or you can buy a yogurt maker online at retailers such as Amazon or Cultures for Health. You also need a properly calibrated thermometer for the accurate measurement of milk temperatures, and enough glass jars or containers to hold 1 quart of yogurt total.
Whole, low-fat or nonfat milk may be used in this recipe, but don’t use alternative milks, such as soy or almond, which require a different technique.
First make sure to clean all equipment with dish soap and hot water. You do not need to sterilize the equipment. Make sure to heat your jars and/or choice of incubator before placing the cultured milk in them.
Make ahead: The cultured milk needs to sit at room temperature for at least 5 hours and up to 24 hours. The finished yogurt needs to sit at room temperature for 2 hours, then in the refrigerator for at least 6 hours before using. It can be stored for up to 1 month.
This creamy, somewhat tart European-style yogurt calls for a Bulgarian heirloom starter, available at Cultures for Health for $12.99 for two freeze-dried packets; each one makes 1 quart of yogurt. The resulting yogurt can then be reused indefinitely as a starter for future batches. (Alternatively, you can use a commercial yogurt from the grocery store. Just make sure it contains live active cultures.)
Fill a sink or a container large enough to hold a saucepan with a few inches of ice water.
Pour the milk into a medium saucepan with a thermometer clipped to the side, positioning its top away from the hot metal. Gradually heat the milk over medium heat to 180 degrees, stirring occasionally with a wooden or metal spoon. Keep the milk at a steady 180 degrees for 15 minutes, stirring frequently and adjusting the heat as needed, to evaporate some of the milk’s liquid. You’ll notice light bubbling and a small decrease in the level of milk.
Transfer the saucepan to the ice-water bath (with the thermometer still attached), making sure the water doesn’t spill over the sides of the saucepan. Stir the milk occasionally as it cools. Once the milk temperature drops to 120 degrees, transfer the saucepan to the counter to cool further.
Once the milk reaches 115 degrees, transfer 1 cup of it into a small bowl, along with the starter; whisk thoroughly until well incorporated. Immediately return the cultured milk mixture to the remaining warm milk in the saucepan, whisking so the cultures are distributed evenly.
For a yogurt maker: Follow the manufacturer’s directions for incubating the cultured milk.
For a Thermos: Warm the inside of the Thermos with hot water, then let it drip dry. Transfer the warm cultured milk to a pitcher or large liquid measuring cup with a spout. Pour the milk into the Thermos, then seal the container and place it in a warm spot. Let it sit at room temperature, undisturbed, for at least 5 hours. At that point, check to see whether the mixture has set to form yogurt. If not, reseal the container and let it sit at room temperature, undisturbed, for up to 12 hours, checking every hour. For yogurt that is more tart, leave the milk in the Thermos longer, up to 24 hours.
Transfer the yogurt to whatever jars you’re using. Seal them and let them stand at room temperature for 2 hours. Then transfer the the jars to the refrigerator to rest for at least 6 hours before serving.
For an insulated cooler: Fill it with a few inches of water heated to between 110 and 115 degrees; add warm or cool water to reach the desired temperature.
Transfer the warm cultured milk to a pitcher or large liquid measuring cup with a spout. Pour the milk into the jar(s), then seal them and place in the warm water. Close/cover the cooler; let it sit, undisturbed, in a warm spot for at least 5 hours. At that point, check to see whether the mixture has set to form yogurt. If not, reseal the container and let it sit at room temperature, undisturbed, for up to 12 hours, checking every hour. For yogurt that is more tart, leave the milk in the cooler longer, up to 24 hours.
Transfer the jars of yogurt to the counter; let them sit at room temperature for 2 hours. Then refrigerate them for at least 6 hours before serving.
Makes 4 to 8 servings (1 quart).
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