We eat a lot of yogurt in our home, and so when our friend Mathieu taught us a cheap way to make our own we were all ears. You can buy yogurt culture in most health food stores (a common brand is Yogourmet), but do the math and it works out to be only slightly cheaper than buying the yogurt available in those same stores, likely not a coincidence. Buy the culture wholesale and the price drops to about 1¢/litre, meaning your yogurt is essentially the same cost as an equivalent volume of milk (around a third to a half the price of yogurt where I live).
We buy yogurt culture online from Glengarry Cheesemaking in Ontario. The trickiest part is learning how much yogurt culture to add. Glengarry sells the culture in packages of 60 grams, which they say is enough for 60 gallons (~230 litres), and you’re supposed to use ¼ tsp per 3-4 gallons (12-15 litres) for a “small” batch, which works out to about 1 gram (or 1/50 tsp) per litre of milk.
I currently use a 1/32 tsp measuring spoon to measure the culture into a ½ litre jar. (This is traditionally called a “smidgen”, and it came in a set that also included a 1/16 tsp measure, or “pinch”, and a ⅛ tsp measure, or “dash”). I’ve also done this by eye on the tip of a butterknife; after a few tries you get the hang of it. If the yogurt is too thin, use more culture; if too thick, use less. If it doesn’t work at all, you probably added the yogurt culture when the milk was too hot.
Method 1: Stovetop
You’ll need a thermometer capable of reading temperatures from 40°C to 85°C, and a large thermos able to contain the jar you want to make yogurt in with lots of volume left over.
- Heat milk to at least 85°C
- Allow to cool to between 40°C and 45°C
- Pour into glass jar and stir in small amount of yogurt culture
- Place glass jar into a large thermos filled with water at 45°C
- Let sit at least 4-7 hours (without moving or shaking the container), or longer (eg. overnight)
Method 2: Electric Pressure Cooker
After years of making yogurt on the stove, we bought ourselves an Instant Pot model with a yogurt making option, which makes this process even simpler. I wouldn’t buy one just to make yogurt (there are cheaper options for that) but if you’re buying one anyways and eat lots of yogurt I’d definitely suggest getting a model with this feature. No thermometer or thermos is needed with this method.
You need to use a mason jar since they’re made to withstand heat. I use four 500 mL jars, since they fit well inside our 6 quart Instant Pot. If you have to force the lid down, the jar will be under pressure and might break. Don’t use the “quick release” method to release the pressure either; that causes the jar to cool down too fast, which will also break it. Just let the Instant Pot cool until the pressure is released naturally (about 20 to 30 minutes).
- Place steaming rack and 1 cup of water into the Instant Pot
- Fill mason jars up to the ring underneath the threads with milk, and firmly screw on a lid
- Place mason jars into the Instant Pot and set to “Steam” for 1 minute with the regulator on the lid set to “seal”
- When cycle completes, turn the pot off, and wait until it cools down to room pressure (the “natural release” method)
- Remove the jars, and wait for the milk to cool to under 45°C (or simply until the jar is no longer warm to the touch)
- Stir in small amount of yogurt culture and seal the jar again
- Place jars in the Instant Pot (no need for the steaming rack or any water)
- Set to “Yogurt”, and let sit 4-7 hours (without moving or shaking the pot), or overnight
It’s also possible to simply pour the milk into the Instant Pot and transfer it to jars once the entire process is complete, as described in the manual, but I prefer to use jars from the beginning to simplify cleanup.