Yogurt, like any health food or any fermented food made at home, has collected a lot of myths around it. Let’s try to replace those myths with facts and common sense.
Myth: Greek yogurt is yogurt that’s strained.
Almost any recipe for homemade Greek yogurt will tell you this. But most store-bought brands of Greek yogurt are not strained. And in Greece itself, strained yogurt is only one way traditional yogurt was made—and not the most common one.
So, it’s best to think of Greek yogurt simply as yogurt that’s thicker than most. There are several ways to achieve this, including a couple of ways much simpler than straining.
Myth: French yogurt is creamy because it’s made in the cup.
Isn’t most homemade yogurt made in small containers? And does that make it creamy? No. The French yogurt you can buy is simply yogurt that’s thicker and creamier than most. And just as with Greek yogurt, this can be achieved in several ways.
In fact, commercial French and Greek yogurts are often made with the same ingredients and methods. They could just as well be labeled either way!
Myth: For yogurt to be yogurt, it must contain two particular bacteria species.
When yogurt was first developed as a commercial dairy product, it was made with just two bacteria species isolated from the many found in traditional yogurt. So, when U.S. government regulators created a standard definition for this product, they based their definition on those two species. As a result, any product today sold in the U.S. as “yogurt” must by law include those two, no matter what other species it has.
But this has nothing to do with yogurt as a traditional food. As long as you add enough lactic acid bacteria of any species to regular milk, it should sour and firm up as some sort of yogurt.
Myth: If you use store-bought yogurt as your starter, you can’t keep taking yogurt from each batch to start the next.
Starting originally with commercial yogurt, neither my wife nor I have ever found a limit to the number of times we can use yogurt from one batch to start another. Contrary to claims, you absolutely do not need an “heirloom” yogurt to do this.
If your culture loses strength, the culprit may be temperature. The bacteria species in commercial yogurt are selected to be most active at temperatures over 100°F, so incubating at lower ones may gradually weaken your culture. And as you’d expect, temperatures too high can do the same.
Though this is strictly optional, you can ensure consistency by starting each time with your favorite commercial yogurt. You don’t need more than a tablespoon of it to make a large jar of your own, and the opened tub should keep for at least a month in the refrigerator.
Myth: You can cut incubation time in half by doubling the amount of yogurt you use as starter.
Not nearly! Incubation time is less affected by starter amount than by fermentation speed, which is based on the bacteria’s doubling time—the time it takes for the bacteria population to double. That time varies by species and by temperature, but as an overall ballpark figure for yogurt making, I figure it at about an hour.
So, let’s say you add one tablespoon of yogurt to milk and quickly warm this culture to a typical temperature. After one hour, the bacteria population will have about doubled, giving you the equivalent of two tablespoons of starter. Say you now mix a second culture but this time add two tablespoons to start it. The remaining incubation time of both cultures will be the same!
In other words, doubling the starter will save you only about an hour of incubation.
Myth: Milk must be heated high and then cooled back down before adding the yogurt starter.
Many people believe that this preheating, or scalding, is needed to kill off competing microbes. But assuming your milk is pasteurized and reasonably fresh, nothing in it is going to catch up with the bacteria population you’re adding with your starter. Those bacteria themselves will discourage anything else from settling in.
There’s another purpose to scalding, though: It alters some of the milk protein so there’s more of it to help firm up the yogurt. But this is only one way to increase firmness, and it’s not the most efficient. Frankly, I don’t advise even considering it unless you’re making low-fat or nonfat yogurt, which tend to be runny. Otherwise, it’s not worth the trouble.
Instructions for some electric yogurt makers tell you to scald the milk, while instructions for others omit that. This does not mean that one yogurt maker needs a different method than another. The difference is just in the instructions, not in the yogurt makers! You can always choose not to scald.
Myth: If your temperature is more than a few degrees off, your milk won’t ferment.
The heat-loving bacteria in commercial yogurt will stay active in anything from room temperature to around 130°F (or 55°C), where they may start to weaken or die off. Within that range, the question isn’t if the bacteria will keep fermenting your milk, but how fast.
Every bacteria species has an optimum temperature, and the farther you deviate from that—higher or lower—the more you slow it down. But the difference has to be extreme before activity stops entirely.
By the way, the common warning that temperatures above 120°F (or 45°C) will kill your bacteria is not valid for the heat-loving bacteria in commercial yogurt. Some might even survive past 140°F (60°C)—though I haven’t felt a need to test that.
Myth: Yogurt bacteria feed on lactose, so you can’t make yogurt from lactose-free milk.
While some yogurt bacteria feed on lactose—milk sugar—they can all feed on less complex forms of sugar. At the same time, some or all of the lactose in lactose-free milk isn’t actually removed—it’s just broken down into some of these simpler forms.
So, lactose-free milk always has some kind of sugar the bacteria can feed on. If it didn’t, it would be too bland to drink!
Don’t be confused by the name lactic acid bacteria. Lactic acid is what these bacteria produce as waste, and they don’t need lactose to do it.
Myth: Yogurt making needs bacteria that ferment milk and milk alone.
If I told you how many decades I believed this, I’d be giving away my age. But the truth is, yogurt is made with lactic acid bacteria of the very same species found in naturally fermented pickles, sauerkraut, and sourdough starter—though it’s usually made today with far fewer species than are in those other foods.
Myth: Yogurt is probiotic, so it’s good for gut health.
This is true to a point, of course, but not as much as believed. Yes, commercial yogurt with live cultures—as well as any homemade yogurt started from it—will contain around two to six bacteria species that are good for your gut. But traditional yogurt—just like naturally fermented sauerkraut, pickles, and the like—will have some or all of those species plus dozens more!
So, the yogurt you buy, and the yogurt you start from it, does not rank that high on the probiotics scale. And ironically, the same goes for yogurt made from probiotics supplements, which might provide only marginally more species, or only a single one!
Now, if you’re eating a variety of naturally fermented foods, or even just raw, whole fruits and vegetables, you might not need your yogurt to supply a wide range of bacteria. But in case you do, I’ll tell you how to easily make your own full-spectrum probiotic yogurt from scratch—with no need of an “heirloom” yogurt as starter.
Myth: To boost its probiotic value, yogurt should ferment for 24 hours, or 36.
If you ferment milk with lactic acid bacteria for long periods at anywhere near typical incubation temperatures, you will get massive population growth at first. But this will be followed by leveling off and then massive die-off, as the population outstrips its food supply or is finally overwhelmed by the lactic acid it’s producing as waste.
Advocates of long ferments generally back up their claims with theoretical calculations based on growth rates in ideal conditions—not in the real world, where growth is never limitless! They may also cite bacteria counts from lab tests, not mentioning that those tests count dead bacteria along with the living. And their recipes often include a stabilizer like inulin, which makes sure that later batches firm up even if no bacteria survived the first.
For greatest probiotic strength, a culture should be warmed only as long as the bacteria are still multiplying faster than they’re dying—then chilled before that’s reversed. Warming for 24 hours or more is a recipe for crippling a culture.
Myth: Any animal or plant milk can be made into yogurt.
To make true yogurt, the milk must have proteins that react to the acid produced by bacteria, causing the proteins to link up in a firm mesh. Animal milks have such proteins, but most plant milks do not. Most so-called dairy-free yogurts, even if soured by bacteria, are actually puddings firmed up with thickeners or stabilizers.
For that reason, this book will focus on yogurt made from regular dairy milk—though at the end, I’ll share one recipe for honest-to-goodness vegan yogurt.
Myth: Saturated fat is bad for you, so you should stick to low-fat or nonfat dairy—including yogurt.
That has been standard dietary guidance since the 1980s. But the recommendation was based on studies of saturated fat in general, not in specific whole foods, which may in some way change or balance its effects. (In other words, saturated fat in meat could be a whole lot worse for you than saturated fat in milk or yogurt.)
Research since then on dairy products has failed to show that full-fat dairy is bad for your health, and in fact has suggested the opposite. Many nutritionists now call for narrowing the original advice or discarding it altogether.
Obviously, the extra calories in full-fat dairy can lead to weight gain. But people who save calories from fat will often make it up in refined starches and sugars, which can be worse. So, avoiding full-fat yogurt may only deprive you of the tastiest, most satisfying, most natural, and even healthiest form of yogurt.
