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Making your own yogurt at home is an easy and surprisingly forgiving process. Generations of industrial food consumption have convinced us that some foods, most foods, need to be made by professionals in commercial kitchens and rigorously controlled environments. I take issue with this thinking, and as a rule of thumb, frequently remind myself that anything humans have been making for thousands of years without special equipment or sanitation can be made in my own kitchen. And you can make it too, I promise. This is the way with fermented pickles, yogurt and cheeses, wild-yeasted bread, and some basic charcuterie and meat preservation.
Making yogurt is a way to preserve milk and extend its shelf-life
I buy milk from Costco, two gallons at a time in my house. Every so often, sickness or vacation will disrupt our normal milk consumption and leave me staring down the expiration date on a glut of milk in my fridge. And when that happens, I extend its shelf life by making yogurt (and sometimes, ricotta).
Milk is truly a fascinating thing. Having young kids, I have had years to observe and ponder this unusual pearly substance in its many forms; the sippy cup abandoned behind the couch for days before it is found, milk mixed with stomach acid before being…. well never mind that’s gross. Did you know that if you do nothing but leave a cup of milk out overnight it will “sour” and thicken and turn into yogurt? Even after it is pasteurized and all the natural bacteria and enzymes in the milk have been killed! How? Turns out it takes a special enzyme to break down lactose. An enzyme that most bacteria take a while to develop or produce except the abundant lactobacillus. This gives lactobacillus a head start from all the other microbes that may cause you trouble and during that headstart lactobacillus digests the sugar in lactose and increases the acidity of the milk (“souring”) making it harder for bad microbes to grow in it then too. It’s like milk comes with a built-in preservation system.
And what is really incredible…what keeps me up at night considering our place in the universe is this: If it weren’t for us humans doing strange things with foods that no other animals do (removing milk from a mother’s body of another species and storing it, harvesting and milling grass seeds, juicing fruit, chopping and salting meat and then packing it into an intestine and hanging it for a long time, etc), these microbes would never have a chance to perform their greatest magic tricks. It makes me wonder if the bacteria are working for us, or us for them, or if it’s just a coincidence that all the pieces found each other. And all these amazing bacteria that effortlessly turn the milk into yogurt and cheese, (and make wine and beer, soy sauce and kimchi, etc), they are all just sitting invisibly on nearly every surface in your kitchen and garden and floating through the air we breathe, just waiting to go to work! Now, I’ve heard people (vegans) tell me that it is unnatural to drink another animal’s milk because no other animal does it. I am not convinced.
Here’s another interesting thing about milk and lactose. Most adults worldwide lack the enzyme that breaks down milk (lactose intolerant). Only in Northern Europeans and Scandanavians and their descendants is lactose tolerance the norm. But fortunately for the majority of lactose intolerant adults, bacteria in yogurt do the work for us, both in the yogurt and in our bodies! Lactose is water soluble so it lives in the watery part of milk, aka the whey. When yogurt (or cheese) is drained and the curds are separated from the whey, most of the lactose is removed and what remains gets broken down by the bacteria. Greek Yogurt is extra thick and creamy because the whey is drained out of it. This is why lactose-intolerant adults can usually tolerate cheese and yogurt.
The Yogurt-Making Process
The process of making yogurt is simple. First, milk is heated to a low simmer, 180F-206F. This effectively kills any undesirable bacteria that may be in it. Meanwhile, sanitize all the utensils and containers that you will be using in a hot oven or pot of boiling water. Once the milk has been heated, then you cool the milk down to approximately 110 F, the ideal temperature for the good bacteria that you are going to add. Inoculate the milk with the good bacteria, aka a yogurt starter. You can use store-bought or homemade live probiotic yogurt from your fridge or even probiotic capsules (emptied), or you can purchase a special heirloom yogurt starter. Let the milk and starter sit in a warm place for 4-12 hours to thicken. Strain to thicken more, if you want to. Refrigerate and enjoy for up to 10-14 days.
I use an Instapot to make yogurt. My Instapot has a yogurt-making setting that maintains the ideal temperature for the 4-12 hours that it takes to thicken the yogurt. This makes it downright impossible to mess up but does extend the prep time by 1-2 hours because it takes so long to heat the milk and cool it back down. If you don’t have an Instapot, no worries, you can make yogurt in a covered heavy pot, and a warm place like a sunny counter, a warm (but not hot) oven, or next to your fireplace.
A note on sanitation
You may be wondering, if milk will turn to yogurt without doing anything, why bother with heating and cooling milk and trying to maintain a warm temperature? That’s a fair question. The answer: with a minimal amount of intervention, you will end up with a better-tasting and safer final product. The strains of bacteria that create yogurt originated from the warm climates of the Middle East, Mediterranean, North Africa, and India where milk would spoil quickly if left out. These bacteria are thermophilic (heat-loving) and produce a tart, thick product relatively quickly in temperatures up to 113 F. The strains of bacteria that make buttermilk, creme fraiche, and sour cream are mesophilic. They like cooler temperatures, 85 F is ideal but cooler is ok too, and those products ripen over longer periods of time in places where the milk goes bad more slowly because it is colder. The window of time that milk is unrefrigerated but not yet acidified by the bacteria, is an opportunity for undesirable bacteria to gain a foothold and create off flavors or worse. We heat the milk to destroy any undesirable bacteria that may be present in the milk before make yogurt. We sanitize storage containers and utensils to ensure that we don’t introduce pathogens into a safe finished product. Salmonella and e.coli may not have any effect on the yogurt-making process or taste, and yogurt may not be its ideal environment for growing, but it could still make you sick if it happens to be in it. If you travel to India or Africa, you will likely encounter yogurt that was made the old fashion way without sanitizing utensils or heating the milk, even using raw milk… and, not surprisingly many travelers get sick. And not just travelers get sick, locals do too. In short, the goal of fermented foods is to apply some control over which strains of bacteria get in, it’s not a free for all, and heating the milk and sanitizing utensils will ensure that.
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Homemade Yogurt
- Prep Time: 2 hours
- Total Time: 10
- Yield: 8 cups 1x
- Category: Dairy
- Method: Fermented/Cultured
- Cuisine: World
- Diet: Gluten Free
Description
Homemade yogurt is surpringly easy to make and a great way to extend it’s shelf life.
Ingredients
8 cups milk (any type, see note)
1/2–1 cup heavy cream (optional)
2 Tablespoons Store bought or home-made Yogurt with live active bacteria (see note)
Instructions
1) Fill a large pot 1/2 full of water, submerge your storage containers and any utenisiles you plan to use (tongs, heat proof spatulas, whisk, or measuring cup with spout, large spoons). Bring this pot of water to a boil. Dip your thermometer probe into the boiling water for a couple of seconds. Remove all utensiles from the pot (I use tongs for this) and transfer them to a clean towel on the counter to air dry. Meanwhile:
If Using an InstaPot to Make Yogurt
Make sure all parts are clean, including the lid and gasket.
Pour the milk into the inner pot. Cover it but leave the vent open. Set the Instapot to “Yogurt” and adjust to the highest position “Boil”. It will begin to heat the milk. This will take about 1 hour. It will beep and turn off when it has “sufficiently” heated. Open the Instapot (it may not be actually boiling), stir the milk and either use your probe thermometer to check the temperature or (if you don’t have one, and I highly recommend you do) visually inspect that the milk is actively steaming. It should be 180 F or higher. You may need to extend the heating time for another 5 or 10 minutes.
Now, pour about 1 cup of milk into a liquid measuring cup and remove the inner pot and place it on the counter or on your burner with the burner off to expedite cooling. Let the milk cool back down to 110 F. This will take about another hour. If you want to speed it up, you can place the pot into a larger pot with ice water and stir the milk occasionally.
The 1 cup of milk that you set aside in the measuring cup will cool faster than the large pot. Once that has cooled to 110 F, stir the yogurt into the 1 cup of milk to inoculate it, and let it sit while you wait for the rest of the milk to reach the target temperature.
When the large pot of milk has reached 110 F, stir in the cup of inoculated milk. Place the milk back into the InstaPot, cover it the vent open, and set it to “Yogurt” for 4-10 hours. The longer it sits the tangier it will be.
If Using the Stove Top:
Pour the milk into a pot (approx 4 quart size) with a lid. If you have a ceramic enameled cast iron brazier or dutch oven, that will work the best as it maintains a warm temperature over a longer period of time. Cover the pot and bring it to a low simmer over medium heat. If you boil the milk over high heat it will likely scald on the bottom. Check the milk every 5-10 minutes, stirring gently and checking the temp. If you do not have a probe thermometer, see note below. When it reaches 180 F, remove the milk from the heat.
Now, pour about 1 cup of milk into a sterilized liquid measuring cup and set aside. Let the milk in the pot cool back down to 110 F. This will take about another hour depending on the pot used. If you want to speed it up, you can place the pot into a larger pot with ice water and stir the milk occasionally.
The 1 cup of milk that you set aside in the measuring cup will cool faster. Once that has cooled, stir in the yogurt and let it sit while you wait for the rest of milk to cool.
When the large pot of milk has reached 110 F, stir in the cup of milk that you inoculated with yogurt bacteria. Cover the pot. Place it in a warm place (in front of sunny window, on your hearth, or a warm but not hot oven that has been turned off) or if you don’t have any of those things, wrap the covered pot in a couple of bath towels to insulate it. Let this inoculated milk sit for 6-12 hours. The longer it sits the tangier it will be.
3) Store your yogurt in the fridge for up to 14 days.
Home-made yogurt in the Instapot.
After 6-12 hours, the milk will be thick. You should be able to lift a spoonful out and it will maintain its shape. You can either strain it through a fine mesh sieve for Greek Style yogurt (several hours or overnight in the fridge) or whisk it vigorously to smooth out any lumps and transfer it right away to your sterilized containers. Cover and refrigerate the yogurt for up to 14 days. It will continue to get tangier in the fridge.
Notes
Selecting Milk For Yogurt
You can use any kind of lactose milk: cow, sheet, goat, etc. You can use skim, lowfat, whole milk and cream. My preferred combo is 8 parts whole milk and 1 part heavy cream. You can substitute about 25% of milk for milk alternatives like soy or coconut milk without making changes to this recipe.
It is possible to make yogurt from soy or coconut milk and other milk alternatives using probiotic capsules or yogurt cultures but it behaves a little differently and this recipe is not really applicable to milk alternatives. Cultures for Health is a great site for purchasing all different cultures and has information about “Alternative Milks for Making Yogurt“.
Selecting your Yogurt Culture
Your yogurt starter should include lactobacillus bulgaricus and streptococcus thermophilis. The easiest method is to use your favorite store-bought yogurt as your inoculum. You can then use your own batch of yogurt to inoculate the next batch that you make. Store-bought yogurt is readily available. You just need to make sure that it is unflavored and that it “contains live active bacteria” versus “is made with live active bacteria”.
You can also use heirloom yogurt starters, gifted from friends or purchased by specialty stores like Cultures for Health. These starters may be specific to a certain geographic region or family. If you strain your yogurt through a cheesecloth or towel, you can dry the towel without washing it (just a quick rinse with cold water) and then use it to inoculate milk.
You can use probiotic capsules that contain lactobacillus bulgaricus and streptococcus thermophilus. Other yogurt-making bacteria include lactococci, lactobacillus delbrueskii, lactobacillus fermentum, lactobacillus casei, and lactobacillus brevis. Probiotic capsules also contain other strains of bacteria that are known to survive the human digestive system and provide health benefit to us but are not known to make the best tasting or creamiest yogurt: bifidobacteria (from breast milk- acidifies the stomachs of infants before stomach acid is produced), lactobacillus plantarum (makes fermented pickles), lactobacillus acidophilus (native to the intestinal tract) and Lacticaseibacillus rhamnosus (native to the urogenital tract). If you use probiotic capsules make sure that they contain primarily probiotics that turn milk into yogurt and be aware that the end product will be healthful but perhaps not as delicious as it could be if you used only yogurt-making species.
If you do not have a probe thermometer:
If you do not have a probe thermometer, you will need to use your senses to check the milk’s temparature. At 180 F, the milk will be steaming even after you stir it. When left alone, it will be slowly moving in the pot from convection, but not boiling.
Liquid at 110 F is the temperature of an extra-hot hot tub. Check the milk by touch without contaminating it. Wash your hand very thoroughly. You know, sing the Happy Birthday Song, hot water, lots of soap, scrub scrub scrub. Then you either can dip your knuckle in it (not your finger because bacterial is hard to completely remove from under your fingernails). Or you can pour a spoonful over the back of your very clean hand.
I highly recommend having a probe thermometer. Mine is one of my most used kitchen tools.
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