Yogurt is one of those amazing things I took for granted until I learned how to make it myself. I won’t lie, I’m not a huge fan of milk– I find the whole idea mildly icky (a subject for another blog post, surely!) So to take something I already find slightly gross, and turn it into something I love by letting it rot— well, that’s just cool.
After recently learning that a particular brand of “Greek” yogurt I enjoyed obtained its thick consistency through the addition of gelatin, I was ticked. Food labels exaggerate health and nutrition claims left and right– but this was an outright lie about what the product was! Greek yogurt is made by straining regular yogurt; this tedious and time consuming process is costly and reductive in nature, but it results in the thick-and-creamy consistency you expect when you buy Greek-style. To skip that step altogether by simply doubling the amount of artificial emulsifiers is just… not cool. Not to mention that they make up for it in the protein department with evaporated milk powder, and “improve” the flavor with the added-sugar levels of a Gogurt.
After a short consultation with the Google, I learned they were not alone. Cook’s Illustrated has a fantastic review and comparison of the top ten brands of Greek Yogurt available at their website to subscribers. And it’s pretty grim. Some are worse than others, but too few are the real thing. I started to get curious about how yogurt was made in the first place– and why all these brands were having such a hard time pulling it off! This led to a few more rather enlightening discussions with the Google, and by the time I learned which in-store Greek yogurt brands were legit (Chobani and Fage, if you must know) I was intent on making yogurt myself at home.
I’m really glad I did, too. My favorite kind of dishes to cook are the ones where ingredients are simple and few, and being skilled is a matter of understanding the science behind the process. Yogurt is the perfect example of this: all you need to make it is a gallon of milk, and a spoonful of yogurt (leftover from last week’s batch, or store-bought). Even with so few ingredients, there are a plethora of different procedures to follow online. There are, after all, just as many different outcomes when one is making yogurt. You can simply choose one that looks or sounds like what you’re going for and hope for the best– and with today’s world of Food Gawker and Pinterest, you probably can’t go wrong. But if you take the time to ask the “why” and learn whats really going on in that petri dish of sour milk, you’ll never need a recipe again.
There are four steps in the yogurt-making process. Though it appears to be, Step 1 is not necessary for any sort of sanitation purposes– more on that later. Finally, step 4 is the process of straining to separating out the whey and make the yogurt “Greek”, or super thick and creamy. This step is also not necessary– just highly recommended 🙂 .
A Breakdown of the Process
- Step 1: (Optional) Preheat milk to 180 degrees F, just under boiling. Whisk occasionally to prevent a film from forming on top. Remove from heat, cover & let cool.
- Step 2: Add bacterial culture (yogurt starter powder or spoonful of yogurt) when milk is cooled to at least 115 degrees F. Stir well, cover and leave to ferment for 3-8 hours.
- Step 3: Test yogurt for consistency. Stir well. Place in the refrigerator for at least 4 hours to halt fermentation. If not proceeding with step 4, now is the time to add in any fruit, jelly, or sweeteners you want. Transfer to an airtight container and store in the fridge.
- Step 4: (Optional) Line a colander with cheese cloth and set inside a large bowl. Pour the yogurt on top and loosely cover with the corners of the cheese cloth. Set to strain in refrigerator until desired consistency is reached: anywhere from one hour to overnight. In a bowl, stir yogurt with any flavor additions or a splash of milk to smooth it out. Transfer to an airtight container in the fridge.
As you can see, this is no recipe. To call it “loose guidelines” even would be pushing it. Instructions such as “leave to ferment for 3 to 8 hours” don’t exactly ring of scientific precision. Bakers particularly, who rely on explicit step-by-steps and careful measurements, would find these four steps on their own annoyingly vague. There are, however, easy ways to solve for these gaps and arrive at more accurate measurements. Its not a guessing game, or magic: creating yogurt is a science, even if it takes reading essays rather than recipes to truly see that. An understanding of the overall process and all of its variables takes out the guesswork and gives you perfect, homemade yogurt every time, no recipes needed.
The Various Variables
- Time is (now and forever) your independent variable. If you have found a way to change it, please let me know. But what does that ubiquitous capital T stand for in this particular equation? In transformation of milk to yogurt, time is a stand-in for the rate at which the cultures ferment– that is, the speed at which the various yogurt-specific strains reproduce and metabolize– consuming lactose in the milk and creating lactic acid as a bi-product.
- Tartness— that sour flavor that makes it yogurt– is a direct result of the lactic acid produced by all those cultures. Yum! The longer it ferments, the more tart it becomes. The best way to discover your own limits with tartness is to test them– duh. Carefully take tiny tastes throughout fermentation. Keep in mind that it takes a long time in the refrigerator to stop the process (and truly, it only slows it down) so the sourness will increase even after you stir and set it to cool.
- Texture refers to how thick or thin the yogurt is. The general rule is that the loner it is left to ferment the thicker it will become. This is true, but time is not the sole factor in how thick or runny your yogurt is: the type of milk plays a role as well.
- Type of Milk used is completely up to you, and only affects the process insofar as mentioned above. The higher the fat percentage, the quicker it thickens and the thicker it gets. If you want to make authentic greek yogurt, you would use goat’s milk cream. So far, I’ve stuck with cow- I have tried skim, 1%, 2%, and whole milk– next on my list to try is half and half! In addition to affecting texture, the type of milk also (of course) impacts the nutritional values of your yogurt. (Soy or almond milk can be used as well!)
A Few Notes
On Preheating in Step 1: All the yogurt recipes I read online included a preheating step before fermentation. I thought nothing of it– until I started to notice recipes without the step listed. It sounded to me like skipping it could be dangerous– or else why bother? It turns out, there’s nothing wrong with skipping this step if you’re already using pasteurized milk. And you are, trust me– unless you are lucky enough to own a cow (or live in a crazy hippie raw-milk commune in Portland) I’m going to assume you bought your milk at the store. It doesn’t matter whether you grabbed a cheap jug from the corner spot or spent $8 on some fancy “organic” stuff that comes in a compostable carton from Whole Foods– if you bought milk in America you bought Pasteurized milk. This means it has already been flash-heated to kill all harmful pathogens that might be present, at a temperature lower than the 180 degrees of preheating. So what does preheating do? It denatures the proteins: basically unfolding them out of their complex, 4-dimensional shapes and into longer more opaque molecules. It’s the same thing that happens when clear liquid egg white hits the pan and turns white. Heating the milk unfolds the proteins, and this in turn creates a thicker yogurt.
On thickening: if you’re going to strain the yogurt in step 4, you don’t have to worry about how thick it gets during the fermentation step. Straining naturally creates a thick texture on its own, so if you want a non-fat Greek yogurt on the less tart side, you can stick with a low, 3-4 hour fermentation period and strain a runny yogurt. But ,if you’re not straining it and you want it thick and tart, go ahead and let it ferment for 7-8!)
On equipment: there are multiple routes to take when making yogurt. Essentially, you want something that will hold a steady temperature above 100 degrees. You don’t have to buy a yogurt maker- although they do come in handy if you make it all the time. All you need is to keep the temperature at 105 and the warm milk undisturbed. But before you reach for your slow cooker, know that that “low” setting is more than hot enough to kill all your cultures. Some of the expensive pressure cookers have digital settings that can handle the lukewarm temps of yogurt fermentation; my own oven, however, won’t even go below 220. Some people still manage to use their ovens; placed in a well insulated dish inside a preheated (but not off) oven is one method. Many wrap their dish in wet towels to increase insulation, others leave the oven’s pilot light on to help keep it warm. Some even ferment their yogurt using what I like to call the “lazy cat’s” method: setting the dish on top of a radiator, television, or other warm whirring mechanical or electronic device. So long as you test your method first– all you need is a thermometer– you’re pretty much without limits here.
On Whey: you’ll be amazed at how much of this clear, yellow liquid strains out of yogurt. Also called “milk serum”, its the same watery stuff you’ll find sitting on top of yogurt in a package. This may or may not sound completely disgusting to you– either way, you might want to consider saving the stuff. There are tons of uses for this “cloudy, yellow liquid left over after milk curdles”. Lovely.