OK, let’s get something clear right out of the gate: Making Yogurt Is Stupid Easy. No, really. That stuff you spend so much money for at the store? Requires almost no effort to make at home. If you can boil water you can make yogurt. Honest. The one “special” piece of equipment required for this method is a gas oven. If you have an electric oven…well…you probably should go elsewhere for instructions (though I include a possible option for you below).
- Step 1: Acquire your ingredients Grab a container of milk (I usually go for a half gallon but any size you get from the grocery store should work) and a small cup of plain yogurt. Have yogurt you made in a previous batch? That’ll work brilliantly. That’s it. You need no other ingredients (though there are some options you could employ but we’ll get into that later).
- Step 2: Sanitize your milk Sure, your milk is plenty clean. You can drink it, you can feed it to your kids, no one gets sick. Brilliant. But the fact of the matter is that everything you eat and drink most likely carries a few harmful bacteria along for the ride. Usually it’s no big deal as your system will dispatch them with extreme prejudice but we’re about to create an environment that’s intentionally favorable to bacteria so…. Yeah, that’s right, sterilize that bad boy. How does one do that for milk? By dumping your container of milk into a saucepan and bringing the lot up to 180° Farenheit (82° Celsius). Once it reaches that point remove it from the heat. You don’t want this to boil (though if it does it’s not the end of the world), just kill off the bad bacteria.
- Step 3: Let your milk cool Set it aside and wait. Yup, that’s it. You want to wait until your milk has cooled down to 100° F (38° Celsius). Ish. Ish-ish. Anywhere between 90 and 110° is fine, really. This is yogurt, not rocket science.
Step 4: Add your starter culture “Wait wait wait, ” you’re saying, “you didn’t tell me I needed a starter culture!” Weeelll…yes and no. I did tell you that you needed a cup of plain yogurt but I neglected to tell you that this, in fact, is your starter culture. And by that I mean it’s your source of the helpful, GOOD bacteria which are going to make your yogurt. Yes, yogurt is made by—and contains—bacteria. Very friendly little bacteria who sit in your milk nomming away at the lactose (milk sugar) and converting it into lactic acid. Not only does this give your yogurt its distinctive tang it also creates an acidic environment which is not favorable to other BAD bacteria. We like these bacteria. They are our friends. To invite these friends to your yogurt party just stir some of them into your milk. How much, you ask? As I typically use yogurt from my previous batch my answer is, “Not enough for breakfast the day before” as that’s the amount I usually have left. But for those of you who need a more precise measurement I’d say about half of your cup of yogurt will do the trick nicely. Stir or whisk it in and, voila, your starter culture is good to go.</li>
Step 5: Incubate your bacteria  Now that you have your starter culture in your milk you want it to be all happy and active so it’ll make dozens and thousands and millions of other little bacteria friends. You’ve already killed off the bad bacteria so your good ones should have free rein in your milk. All you have to do is to keep it warm… Pour your milk/culture mixture into a container (I usually use the one that the milk came in; no extra dishes!), close it up loosely then place it into your gas oven. Yes, the oven should be off. There’s plenty of residual heat from the pilot light to keep the oven cavity the perfect temperature for your happy little bacteria. Please note that I said to close your container loosely. This is important! As your bacteria convert lactose to lactic acid they produce carbon dioxide as a biproduct. Close your container tightly? You’ll have a mess to clean up. Just sayin’…
Let your nascent yogurt sit in the oven overnight and then, in the morning…</li>
- Step 6: Enjoy the yogurty goodness Yup, that’s it. You now have yogurt.</ul>
There are a few other tips, tricks, pointers which you may need…
- At first your yogurt may seem a bit “loose.” Yogurt is made up of two main parts: whey and solids. The two don’t play nicely together immediately (but it’s still tasty as-is). If this bugs you then there are three things you could do:
- When heating your milk, add a quarter to a half a cup of dried milk to the mixture. This will add more structure to your young yogurt.
- Strain out some of the whey in a colander lined with a double-layer of cheesecloth. This shouldn’t take very long (maybe ten minutes or so). Strain it longer (an hour) for that fancy Greek yogurt that you spend too much for in the store and even longer (4+ hours) for labneh.
- Have patience. It’ll ‘tighten’ up after a day or so. This, by the way, is rarely my selection. Patience? Pshaw…
- Yes, once your yogurt is complete you can add fruit. Heck, go ahead and add jelly/jam. That’s all those store-bought fruited yogurts are anyway: yogurt with jam. I’m a fan of the plain yogurt, myself, so I can’t speak to how well your yogurt will keep with fruit or jam in it. Just to be safe you may want to add it at serving time.
- Your yogurt will keep well for at least a week. Mine never lasts much longer than tha so I don’t know its full lifespan. It is a dairy product so please use your judgment here.
There you go: instructions for making yogurt. See? I spoke truth: it’s stupid easy. Give it a try and let me know how it goes for you.
 By the way, this is the step which all those standard $50+ yogurt makers will perform for you: keeping your bacteria warm. Yeah, that’s about it. If you don’t have a gas oven you can likely get the same effect with a heating pad on low and a blanket, but I’ve not tried it myself so your mileage may vary.