Yogurt (tutorial)

Every two weeks I drive 40 minutes south to pick up a couple of gallons of fresh raw cow’s milk. It lasts around a week fresh, but that’s fine because the boys around here aren’t huge straight-milk drinkers, and I can only eat cultured dairy right now (which has a longer shelf life). So very little of the milk I get is for straight drinking. Instead I turn it into yogurt and kefir! It’s a great way to preserve the milk to last longer (so I don’t have to make that long drive every week!), and it’s a healthful way to get our dairy intake. We love straight yogurt (and I like straight kefir too!), and kefir and yogurt smoothies are a huge hit here and a staple breakfast or lunch during the summer.

Here is how I make yogurt with raw milk, but even if you use pasteurized, you can follow along, and I’ll explain the one difference you will want to make in the directions:

First start with delicious creamy milk:

You can’t really see the creamline very well in this picture, but if you squint and strain really hard, you’ll see it around the level of the word “Raw” on the label. Yep, summer pasture milk is deliciously rich and creamy :-).

And a yogurt starter. Essential part of yogurt making:

This is reserved yogurt from my previous batch. You can buy any old plain yogurt from the store for your starter, but just make sure it is PLAIN yogurt (not flavored, sweetened, etc.) and most importantly, that it states it has “live active cultures.” Once you make a batch of your own, you can reserve some of it to use as your starter next time. General recommendation is to occasionally replenish your starter by starting over with a store culture, to keep those bacteria strong and vigorous. I do this periodically. I’d like to say it’s because it’s intentional and I have a set schedule of how frequently I do this, but honestly, it’s whenever I eat up all the yogurt without remembering to save a starter ;-). So every 2 months, maybe?

When making yogurt, the basic idea is:
(1) Heat milk to about 105 degrees or 110 degrees so that the good bacteria (the starter) will grow happily.
(2) Add starter to heated milk.
(3) Keep at this temp for a set period of time (4 – 24 hours), while bacteria proliferate – this is called “incubation.”

Now, this is the basic outline for making yogurt with raw milk. And you’ll find different suggestions for ideal incubation temperature, but I find 105 degrees to be great. With raw milk you do NOT want to heat higher than about 110 degrees or you risk destroying enzymes and good bacteria, and therefore might as well have used pasteurized milk anyway (yes, I’ve accidentally done it once!). Now, if you don’t want to go the raw milk route, I respect that choice, and by all means get pasteurized! But if you already paid the premium price for raw milk, keep it raw!

If you use pasteurized milk you’ll need an extra step in here. When you heat the milk, you first need to heat it to 185 degrees to kill bacteria (Yes, even pasteurized milk has bacteria! Pasteurization slows bacterial growth and discourages pathogens, but only UHT-pasteurization actually kills the bacteria fully. But UHT-pasteurized milk – aka “ultra-pasteurized” milk also doesn’t support growth of *any* bacteria, so it can not be used successfully for making yogurt. Don’t bother trying.) This allows the yogurt starter to culture on a “clean slate,” rather than compete with other organisms. Because raw milk contains beneficial enzymes and good bacteria to help balance the bad, this step is not needed for raw milk yogurt (strange but true).

After heating the pasteurized milk to 185 degrees, you then have to cool it to somewhere betwee 90 and 120 degrees, which is the range at which lactobacilli proliferate. If you add the starter culture to the milk before it cools, you’ll kill the culture and the milk won’t turn into yogurt. These are live organisms we’re dealing with here; be nice to them! 120 degrees is too high for raw milk yogurt, as enzymes and some bacteria start to die at that temp, so keep that in mind. That is why 105-110 degrees is recommended above. Cooling the milk takes a while, but when you figure that you got your pasteurized milk from the local store instead of driving to the ends of the earth to obtain licensed raw milk, just consider that you got the better end of the deal, time-wise ;-).

Anywho, off the pasteurized yogurt tangent. . . back to our regularly scheduled programming. So that’s the basic outline, and now some pictures to show you more precisely what I do:

Making Yogurt

You want to carefully heat the milk to about 105 degrees (or 180 degrees for pasteurized, see above) so it heats evenly and doesn’t scald, burn, etc. The best option, in my opinion, is a double boiler. Here is my set-up:

A few inches of water in the lower pan, with the other pan set above (water not touching upper pan, as per usual double-boiler practices). Candy thermometer inserted to measure temp, and a metal spoon to stir periodically, so the milk heats evenly. I don’t add the spoon and thermometer until the water in the boiler comes to a boil with the lid on. At that point I remove the lid and add the thermometer and spoon. The first time or two you make yogurt it will take more time and effort. You won’t know how long your particular amount of milk in your particular pot will take to come to a boil (and how long it will take to cool, if you use pasteurized milk). Yogurt was a process the first couple times I made it. Now I know much better what happens when, and it is very much a brainless thing to make, while I’m puttering around the kitchen doing dishes. Give it three times or so, and you won’t feel stressed.

I tried this brilliant method of heating the yogurt in jars, and I love it in theory. Hated it in practice. I must have the Curse of the Broken Yogurt Jars or something. I would estimate that 2 out of 3 times I made yogurt that way, one of my jars would break. I carefully padded them, spaced them apart, etc., etc. I have no idea what my issue was. But it’s a great method for those who don’t have the Curse of the Broken Yogurt Jars. But I gave up and went with the double boiler method, once I broke my fourth or fifth jar. And it really works well this way.

Once the milk is heated to 105 I pull it off the burner (don’t forget extra step of heating and cooling if the milk is pasteurized). Then I ladle it into my jars. I make a gallon of yogurt at a time, and do it in two half-gallon jars. I used to do quart jars, which I think most people would prefer, but I was trying to use fridge space more efficiently, and I have loved switching to this jar size. Some people say to sterilize the jars, others (including me) just wash them out really well with hot water and soap and let air dry. But for the sake of any lawyers you might hire, I DEFINITELY told you to sterilize! Do what I say, NOT what I do! (I would definitely sterilize for something like pressure canning, but that’s a whole other ballgame, folks.)

Then I add my starter. Ideally you want the starter at room temperature before adding to the milk. This helps keep the milk warm, rather than cooling it with a fridge-temp starter. Honestly I’ve used cold starter and it survived, but since leaving it out to warm, I’ve gotten more consistent smooth consistency from the yogurt. I’m not sure if that’s related, but it might be. I use 4 tablespoons of starter per 1/2 gallon of milk. More starter is not necessarily a good thing. You want to give your bacteria space to proliferate, so don’t dump in a ton of starter and think you’re helping matters.

Then you want to stir the yogurt gently to distribute the starter. Don’t go too vigorously. I’ve read several places that you could harm the bacteria. I have no idea if this is true. But go gentle anyway, because why not? I use a butter knife which is DEFINITELY STERILIZED (*cough* (That was a sterilized cough into a face mask.)) to stir the starter into the milk.

Now is the fun part. You get to decide first of all, how long you want to incubate. Basically, you can do anywhere between 4 and 24 hours. The longer you culture, the firmer the yogurt will be, which is a good thing, as homemade yogurt – especially raw yogurt tends to be runnier than storebought yogurt. The longer you culture, the tarter the yogurt will be too. (Incubation temperature also has an influence on these variables.) I culture the full 24 hours because I can’t have lactose right now, and the lactobacilli in the yogurt (fancy name for “yogurt bacteria”) eat up all the lactose if they are cultured the full 24 hours. It’s really not that much more effort to do a long incubation, but it’s up to you. I think even when/if I can have lactose, I will probably still choose the 24 hour culture, because it’s just a matter of 2 switches of hot water, and the yogurt is much firmer this way.

Everyone has a different method of keeping yogurt at the right temperature for incubating. Frankly, use what appeals to you and make sure to test temps the first time or two, to make sure the yogurt is still above 90 degrees (but not over 110 degrees for raw milk – or over 120 for pasteurized) by the end. You can use the pilot light on an oven, a dehydrator, and a few more obscure options, but my favorite is a cooler with a vessel of hot water. It works great and is low tech.

I line the cooler with a towel for padding, extra insulation, and so we don’t have plastic melting from direct contact with the hot water vessel in the center. I place boiling water in a stainless steel canister in the middle, and the yogurt jars on either side. This same set-up works with two quart sized jars on either side of the stainless steel vessel (4 quart jars total). After placing everything in and making sure items are spaced and not bumping, then I fold the towel over the jars, to insulate all that heat, and then close the lid. You don’t want the folded-over towel dipping into the hot water, or you end up with a soggy towel mess.

If you’re only culturing for 4-8 hours, you’re probably good to go and don’t need to switch out the water. But for a 24 hour culture I try to switch out the hot water for fresh boiling water every 6-8 hours, to keep things warm enough. Keep the lid open as little as possible while switching out water, to preserve heat! The first time you do this, test the temp at the end of the incubation period, to make sure it stayed warm enough; after that, you can assume it’s fine for future cultures. At the end of the culturing time, transfer your jars of yogurt to the fridge, chill, and enjoy! I like flavoring yogurt with a little vanilla and raw honey.

And that’s how you make yogurt!


4 Comments (+add yours?)

  1. hannahpi
    Jul 05, 2011 @ 13:42:22

    Oh how I miss yogurt.
    They only have the sugary kind here.
    And I squinted. Hard. Not seein’ the cream line.


  2. susanegk
    Jul 05, 2011 @ 14:09:07

    Yeah, it’s really hard to see. Clearly you need to come see it in person :-).


  3. hannahpi
    Jul 05, 2011 @ 14:11:40

    Only to see the cream line, mind you.


  4. susanegk
    Jul 05, 2011 @ 15:20:55

    Right. There wouldn’t be other inducements.


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