Home-made yogurt is both tastier and cheaper than store-bought yogurt, plus it's extremely simple to make; you just have to be patient. You also don't need any special equipment to make the yogurt. All you require is a cooking pot, a (heat-safe) non-metal container big enough to hold the milk, and your stove and oven.
If you also want to drain your yogurt in order to make Greek-style yogurt (which I always do, because it's DELICIOUS), then you'll also need a spaghetti strainer, a large bowl, and a clean tea-towel or pillowcase you're willing to use as a cheese-cloth. The first six steps of this Instructable will cover how to make home-made yogurt. Step seven covers how to drain it in order to make Greek-style yogurt, and step eight contains my favourite ways to flavour home-made yogurt!
Step 1: Ingredients and Overview
- 2 litres of milk (2 quarts)
- 1 small container of plain, store-bought yogurt that says it contains "live" or "active" bacteria on its ingredients list
- A cooking pot large enough to hold all the milk
- A heat-resistant, non-metal bowl/container large enough to hold all the milk
- A whisk if you have one, or a fork and spoon if you don't
- A stove to heat the milk on
- An oven with a functioning oven light to incubate the yogurt in
Further equipment if you want Greek-style yogurt:
- A spaghetti strainer (i.e. a colander)
- A bowl large enough to nest the strainer inside of, with a bit of clearance underneath the strainer
- A clean tea-towel, or pillowcase, or (if you're swanky!) an actual cheese-cloth
The Basic Idea:
Making yogurt consists of sterilizing the milk by bringing it to a boil, letting it cool to a temperature that yogurt bacteria will thrive at, adding a dollop of store-bought yogurt to the milk in order to dose it with the right kind of bacteria, and then keeping the whole concoction at the right temperature for about 8 to 12 hours so the bacteria can grow.
Step 2: Sterilizing the Milk
Depending on how experienced you are in the kitchen, the next step will either be super-easy, or a potentially terrifying, lava-like kitchen disaster. The TL;DR version of this is: You want to bring the milk to a boil.
However! Milk tends to (1) burn on the bottom of the pot before it boils, and (2) boil over the top of the pot INSANELY quickly once it reaches the right temperature.
So first, inspect your pot. Is the metal thick or thin? If it's thick and heavy, then you can probably do what I do: Pour your milk into the pot, put it on a stove burner set to about 3/4 of its maximum heat, and let the milk warm up.
For my stovetop, the milk takes about 14 minutes to boil at that temperature, and although the milk does brown on the bottom of the pot, that doesn't adversely affect the milk's flavour, and I don't have to stir while it's heating. (But I *do* have to soak and scrub my pot to get it clean afterward, however.)
If your pot is made of thin metal, then you need to stir the milk constantly as it heats up in order to prevent it scorching on the bottom of the pot. (Burnt-tasting yogurt would be disgusting! Also, scorched milk is a pain to scrub off the bottom of your pot.) Again, set your stove element to about 3/4 of its maximum value. If your stove is like mine, it should take about 14 minutes to boil.
Now the dangerous, potentially-messy thing you must guard against: When milk finally decides it's at the right temperature to boil, it will very rapidly go from "I'm just a wee bit frothy and bubbly" to "WHOO-HOO! VOLCANO IMITATION!"
Thus, for the sake of your stovetop, watch that pot like a hawk once it starts to look like it's close to boiling. You will literally only have about 3 seconds to pull it off the heat once it starts to foam up.
Once the milk starts to foam up, take it off the heat, and pour it into the non-metal bowl or container you plan to use to incubate your yogurt culture in. The hot milk will sterilize your container.
Please note the container MUST be non-metal because metal self-sterilizes, i.e. it kills bacteria, including our friendly yogurt bacteria that we want to nurture. This is why door handles in institutional settings are often unvarnished metal; after about 8 hours, most of the bacteria on the metal will be dead. (But the viruses won't be, sadly.)
Step 3: Cooling the Milk and Preparing the Oven
Leave the milk to cool at room temperature for about an hour. If you've got a thermometer, you can check whether the milk temperature has gotten down to roughly 40 degrees Celsius (100 degrees Fahrenheit), but you don't have to be exact about this. You want the milk to be roughly body temperature, and an hour should do it, unless the air temperature of your house is particularly hot or cool.
While you're waiting for the milk to cool, turn on your oven light (but not the oven! That would be too hot for our bacteria), and keep the oven door closed to hold the warmth in.
By the way, if you forget to turn on the oven light now, just do it before you put the milk into the oven to incubate. I've made that error, but it has never hurt my yogurt.
Step 4: Dosing the Milk With Yogurt Bacteria
Once your milk has cooled to roughly body temperature, a skin will likely have developed on the surface of the milk. Scoop that skin off and either eat it or discard it. (My husband loves this stuff. I have no idea why, but okay, he can have it.)
Next, you want to plop some yogurt bacteria into the warm, sterile milk so they can start building their yogurty empire for you.
The yogurt bacteria will come from your small container of plain, store-bought yogurt. As long as the ingredient list on the yogurt says it contains "active" or "live" bacteria, it should work.
Put a spoonful of the store-bought yogurt into your milk and whisk it in with a fork (or an actual whisk, if you have one.) You only need one generous spoonful of the store-bought yogurt in your milk. I usually buy the smallest-possible size of yogurt, then use it as my starter culture for three or four home-made batches of yogurt.
Step 5: Incubating Your Yogurt
Now that the milk has been dosed with friendly yogurt bacteria, you need to keep this milk/yogurt concoction warm for 8 to 12 hours. This gives the bacteria time to turn all the milk into yogurty goodness.
Your incubator is just going to be your oven with the oven light turned on to keep things cosy, but not hot. Put your bowl of milk/yogurt into the oven, close the door, and leave it for 8 to 12 hours.
By the way, I find the yogurt is noticeably better if I wait the full 12 hours as compared to only incubating it for 8 or even 10 hours. I've heard of people leaving their yogurt to incubate for a full 24 hours, but I've never had the guts to try that.
Also, a friend of mine's mom used to make yogurt by putting the bowl on top of her old refrigerator. The heat coming off the coils at the back of the fridge were enough to keep the yogurt bacteria happy! I'm not sure that would work with today's more energy efficient refrigerators, but it might. If you don't have a working oven light, you might consider trying this.
Step 6: Enjoy Delicious Yogurt Immediately! Or, Make Greek Yogurt to Enjoy Later
When the yogurt comes out, it will look like this: A white, jelly-like, solid mass with transparent, yellow-ish liquid mixed in with it.
IMPORTANT: If it does NOT look like this, i.e. if it still looks like liquid milk, then discard the whole batch. For whatever reason, the bacteria didn't multiply, and that means the milk will have gone bad and is no longer safe to drink or use in any way. (But don't worry, I've never had a batch of yogurt NOT work -- except for the time my husband turned the oven light off. Guess I should've put an explanatory post-it note on the stove that day...)
The white, solid stuff in your container is the yogurt, of course, and the yellow liquid you see is the whey. Both are perfectly edible. If you don't mind watery yogurt, then you can just mix these two components together and eat/drink the yogurt like this. Lassi, an Indian drink, is made with yoghurt mixed together with all its whey, and then flavoured with cardomom, honey, and either banana or mango puree. It's delicious!
Personally, I love my yogurt thick, so I always drain it to make Greek-style yogurt. The remainder of this Instructable will cover how to drain the yogurt, with the final step listing a few of my favourite ways to flavour my yogurt.
For those of you stopping here, however, I'll note that this yogurt does NOT freeze well unless you plan to blend it again after it thaws (it'd be fine for smoothies, for example.) However, it keeps in the refrigerator very well. In fact, I've heard it will keep for up to a month, although we've never managed to refrain from devouring it for that long. Do note, however, that if you add other ingredients like fruit or fruit juice to the yogurt, you should get it eaten within one week.
Step 7: Draining the Whey From Your Yogurt
Greek-style yogurt is just yogurt with a lot of the whey strained out.
Take your spaghetti strainer (colander) and nest it inside a large bowl. The bowl should be deep enough the strainer doesn't touch the bottom.
Drape whatever you're going to use as your cheese-cloth over the strainer. I used a clean tea-towel, but an old, clean pillowcase would work too. Press the fabric down to make a dent in the centre of the strainer that you can pour your yogurt into.
Pour all the yogurt and whey into the cheese-cloth/strainer. Wait 5 minutes. About half a litre/quart of whey is going to drain out pretty much immediately.
Unless your bowl is very deep, you probably want to pour the whey out now so that the yogurt isn't sitting in a puddle of it. It won't continue to drain very well if it is!
Re-assemble your strainer/bowl setup and wait another 5 minutes. Another 1/4 of a litre/quart of whey will drain off in this time. Pour this away too, and then I recommend you stir your yogurt. By this point, the yogurt next to the cheese-cloth will be noticeably drier-looking than the stuff in the middle.
Now you have a choice: Continue straining your yogurt the easy, laziness-enabled way, or get it strained faster by investing a bit more effort in it.
If you want to do it the easy way, just stick your yogurt/cheese-cloth/strainer/bowl assembly into the fridge and leave it for an hour. Or several hours. I usually boil my milk the night before, let the yogurt incubate overnight, drain off the first ten minutes' worth of whey in the morning, then stick it all in the fridge and go to work. When I get home from work, I have this super-thick, almost crumbly yogurt (called labneh in the middle east) that can be spread on bread.
If you want your yogurt faster, however (and looking like yogurt, not ricotta cheese), then leave it to drain for another 15 minutes, stir, and then decide whether it's thick enough yet. If you want it to match the consistency of store-bought Greek-style yogurt, then you probably want to drain it for an additional 15 minutes after this. The proper consistency occurs after you've drained off about 1 litre/quart of whey, i.e. half the original volume of milk.
Personally, I don't use the whey for anything, but you can add it to smoothies and bread recipes to give them extra protein and calcium. (But be aware of the corollary to that last point -- when you strain your yogurt to make Greek-style yogurt, you are *reducing* the amount of calcium in it. Some of it leaves with the whey.)
Next, my favourite recipes for flavouring my yogurt!
Step 8: Some Suggested Flavours for Your Yogurt
My favourite way to eat home-made Greek-style yogurt is with mashed blueberries (looooots of blueberries) and brown sugar.
I put about 2 cups of frozen blueberries in a bowl with a few tablespoons of brown sugar, then microwave it for 3 minutes to make the blueberries nice and squishy. Then, of course, I squish them. Next, I add a cup of yogurt, mix it in well, and devour! (The yogurt is warm when you prepare it this way, but I've come to prefer it like that.)
My husband's favourite recipe is quite different, but pretty neat. We make ginger syrup, and he mixes it with his yogurt. The ginger gives the yogurt a nice, light flavour but with a bit of burn. It's an exotic alternative to vanilla yogurt!
To make a batch of ginger syrup, combine a cup of sugar with a cup of water, then grate in maybe a quarter cup of fresh ginger root. Boil everything together to about 225 degrees Fahrenheit, or to the lower edge of the "thread" stage of candy making, then strain out the ginger root. If you find the ginger root is starting to burn and darken the syrup, go ahead and strain it out early, then continue boiling the syrup to the desired consistency.
Add a few tablespoons of ginger syrup to a cup of home-made yogurt, mix, and enjoy!
By the way, for those of you (like me) with a minimal number of kitchen gadgets, making syrup without a candy thermometer is a pain, but it's possible. Read this webpage (https://www.exploratorium.edu/cooking/candy/sugar-stages.html) to learn the basics, and then remember you're trying to get to the "thread" stage. (And also remember to be very, very careful, because holy moly, can you ever burn yourself badly with hot sugar syrup!)
Finally, I just recently tried lemonade yogurt (fresh lemon juice and white sugar) and it was yummy! You do need to use very well-drained/thick yogurt for it, however, or the lemon juice will make it runny.
Happy yogurt making! May all your yogurt empires thrive. :-)