My family goes through about a gallon of yogurt a week, give or take. It's a favorite in school lunches, for dessert, for breakfast, for snacks, or in smoothies - we don't give it that often, generally only one serving a day, but it can be pretty much any time of day. The last time I checked on the price of Stonyfield Farms whole milk (so full-fat) organic yogurt, though, it was pushing $5US per quart, meaning a gallon of organic yogurt would run up a tab of about $20 a week! (I suspect the price has gone up since then - it's been a few years since I bought it.) By contrast, a gallon of organic milk runs about $5-6US week, depending on where I can get it and whether it's store-brand or not and what's on sale that week. I can easily buy into the idea of saving $15 a week on yogurt alone.
The way I make yogurt is based on the Girls Guide to Guns & Butter's Crockpot Yogurt recipe, modified to fit my kitchen and needs. Reading it makes it look a LOT more complicated than it really is, and after the first couple of times you'll get into a groove and it'll be a lot easier. Promise. Ready? Here we go!
-One gallon milk (or however much you want to make - I go with a gallon because it comes that way, we use it in a week, and I have quart-sized Mason jars to culture and store it in).
-A couple spoonfuls of yogurt and/or whey (the liquid that often floats to the top of the yogurt) to start a new culture.
-Optional: one packet of unflavored gelatin (Knox or similar) for a bit more thickness (less watery).
For cooking, I use a Dutch oven or soup pot (mine is a 5-quart pot). For culturing and storage, I use 4 quart-sized Mason jars with lids - they don't have to seal tightly, as this isn't "canning;" I just find the size convenient. :-) I also use a half-pint jar if I'm using gelatin as a thickener. Finally, have a few towels handy, as you'll need to keep the jars warm while they're culturing. Oh, and 2 other CRUCIAL implements: a thermometer, and a TIMER. Trust me on this.
Making the yogurt:
|Two gelatin options|
2) Turn your stove burner on low, maybe a bit higher depending on your stove, and heat the milk in the cooking pot to 180F/82C. This is where the timer is crucial, because odds are you won't want to watch the pot and you WILL end up with boiled milk all over your stovetop at some point. I start out by setting the timer for 20 minutes and checking the temperature periodically, with shorter intervals as I approach the 180-degree mark.
|Meat thermometer works great!|
3) Once the yogurt reaches 180F/82C, remove it from the heat and let it cool to about 110F/ 43C; before you can add the yogurt or whey to start a new culture, the temperature must be below 120F/49C or the bacteria that do the culturing will be killed and you'll just have warm milk.... a LOT of warm milk. If I'm using gelatin to thicken (remember, this step is optional!), I put a little of the warm milk from the pot on the stove into the set-aside jar of milk and gelatin, put a lid on the jar, and shake it like crazy before adding it back into the milk in the pot when I begin to let it cool, but you can add it in at pretty much any point if you forget it; just make sure any clumps are broken up.
4) As the yogurt cools, you may notice a skin forming on top. This stuff is perfectly edible and my children literally will fight over it. Seriously, all I have to do is yell, "Yogurt scum!" and children come bounding from wherever they are in the house or yard. I use 2 forks to divide it between them. It can also be served in a small dish (or large spoon) with maple syrup (I also got this from the Girls Guide post.) as a treat. :-) You do want to remove it from the milk, though. I have also discovered that heating the milk makes it digestible for me, so even though I'm mostly dairy-intolerant, I can consume this stuff without a tummy-ache.
5) Once the yogurt is at culturing temperature - cooler than 120F/49C but no cooler than 105F/ 41C, that's when I mix in the new starter. I have the most luck doing this by putting some into a small jar (or using the dregs from a previous jar), adding a ladleful or two of the warmed milk to the jar, and shaking it to mix, and then adding it back to the pot. If I just spoon in the yogurt directly to the pot, I just end up with clumps of yogurt that splash a lot when I pour (next step).
6) Almost done! I put the 4 Mason jars (or whatever jars I have free) in the sink because I inevitably spill some while pouring from the big pot. I fill them pretty much to the top (there's often some foam from the pouring), put lids on them (no need to tighten the lids much), and keep them in a small cooler while the milk cultures. I cover the bunch of jars with a couple more towels inside the cooler to keep the temperature fairly constant for the next 4-8 hours, and voilà! Yogurt! The longer it cultures, the more sour it will taste; closer to 4 hours it has a milder flavor, so you can adjust your culturing times according to your taste - or adjust your expectations according to your culturing time. LOL
Sometimes after this step I'll have a bit of milk left over in the pot; I'll drink it right out of the pot before I wash it, but if I have enough to fill that half-pint-sized jar I used for the gelatin step, I'll use that too!
At this point I just store the jars in the fridge till we serve the yogurt. The girls can dish some themselves from jars this size without help now, and it's also easy enough to dish this into reusable containers to put into their lunches. Sometimes I'll add fruit, sometimes chocolate chips, sometimes I'll use it as a base for a veggie dip, sometimes I'll add some vanilla or even toss some into the blender for a smoothie (I make mine with yogurt and coconut milk - that'll have to be another post entirely). When I get to the bottom of the jar and can't get the rest out, I'll pour in some rice milk (and sometimes a bit of coffee!) and shake it up to make a mini-smoothie before I wash out the jar for the next use.
[Edit: For Christmas this past year, I got an Instant Pot electric pressure cooker with a Yogurt setting that makes it SOOOO much easier to heat the milk without having to worry about boilover. Once the pot beeps, that means the milk is at the desired 180F; at that point I remove the inner pot to cool (and there's no hurry; it can cool in the cooker, although it does take longer, but this feature means I can get the milk started and then go out for most of the day while it cools to about 115F and then keeps it there!).]