Tuesday, October 11, 2011

Make It Yourself: Yogurt

Let's face it: I'm a little crazy when it comes to food. I go out of my way to try unusual things, I eat things most people wouldn't even touch, and I generally just have an absurdly curious appetite. Because of this, I find that one of the things I most often do is make my own food - And I don't mean just cooking up dinner and whatnot, but actually making things from scratch. Cheese, pasta, wine, I'll make it all myself if I've got the time and materials.

Now onto today's topic: Yogurt.

However you want to spell it, it's pretty much the same thing. There are, of course, many different kinds of yogurt, but the process is largely the same. I could go on and on about the different kinds of yogurt that you could make, but for now I'll just give you the basics so you can give it a go.

Yogurt is one of those things that a lot of people don't expect to be able to make at home, but really, it's quite easy. In fact, it's one of the easiest dairy-derived products you can make at home. Now, if you have a yogurt maker, that's all well and good, but I want you to forget about using the mixes to make your stuff. We're doing this from scratch (Well, no so far as in to milk the cow yourself, but you get the idea.).

If you don't have a yogurt maker, don't fret. All you need is a smaller container and a larger container, and either a hot water cupboard or a big cooler. Now, personally, for the smaller container, I find anything about four cups in size is best. For the larger container, just make sure that's it's big enough to fit the smaller container inside, with lots of space for a water bath.

Basically, the idea behind making yogurt is that you want to heat up the milk to just above body temperature and let it culture into yogurt. Of course, doing this straight off is a bad idea, since you never really know what you'll get. It could just be sour milk.

Before we start, you'll also need a couple other things:
• Milk - This is a must, of course. 2% fat or more is better; any less and your yogurt might end up really runny.
• Pot - You need this to heat the milk. It should be twice as large as the amount of milk you're using.
• Starter Culture - If you don't know where to get or simply can't get yogurt culture, the easiest thing to do is just to use some existing yogurt to start things going. Gourmet yogurt works best; I find that cheap tubs of yogurt will give you an extremely sour and unpleasant result which you will most likely end up having to toss.
• Candy Thermometer - While not completely required to make yogurt, it is a recommendation as it makes things easier. Any thermometer with a range from 40-100°C (100-220°F) will work just fine. Your finger also makes a decent substitute, but don't burn yourself.

Step One: The first step in making a good yogurt is to 'scald' the milk, which involves heating the milk to 80°C (176°F) for a couple minutes. In a large pot (At least twice the volume of the amount of milk you're using.), bring one liter of milk (Or however much you're using.) to near-boiling. It's okay if the milk bubbles, but don't let it burn. It's also not a good idea to cover the pot, since although it'll heat faster, once the milk boils it'll foam and overflow. Let it simmer for two minutes.

The purpose of scalding the milk is quite simple: By bringing the milk to near-boiling temperatures, proteins in the milk change shape in a process called 'denaturing'. Scalding the milk also removed any unwanted microorganisms that might be growing in there which could affect the yogurt. If yogurt is made from unscalded milk, you'll get a yogurt with a 'ropey' consistency; that is, the yogurt becomes stretchy beyond recognition, and is slimy on the palette. While similar to the Finnish yogurt viili, this is not the same. You don't want this, trust me.

Step Two: Once the milk is scalded, take it off the burner and cover it. Let it sit (With the thermometer in it, so you can check the temperature.) for an hour or so until it cools down to about 45°C (115°F). While 43°C (110°F) is the temperature you want, by the time you finish with the rest of the stuff it'll be there. Typically, this is the point when flavorings are added. Personally, though, I prefer to leave my yogurt plain so I can add whatever flavors I feel like at the time I eat it. It may be wise to add a little sugar to sweeten it though (NEVER add unpasteurized honey before the fermentation is complete, as it contains live microorganisms and will interfere with the yogurt making process, and can make you very, very sick.).

Step Three: Stir in the starter culture or yogurt into the warm milk until it's mixed through, and pour the mix into the smaller container. In the bigger container, pour in some hot water from the sink. Ideally, this water should be the same temperature as the milk; about 45°C (115°F). You can use your thermometer to check the temperature, or your finger; if it hurts, the water is too hot. With the small container in the large one, the water should be up to the brim, but not tipping over the edges (You don't want to water down your yogurt, or spill.). Cover with plastic wrap or a lid if possible, and store away in your cooler or hot water cupboard.

The culturing process is a neat one, if you're interested in that kind of stuff. Various lactobacillus bacteria (The good kind, of course!) feed on the lactose sugar present in the milk, and turn it into lactic acid. This, in turn, denatures the proteins further, causing them to bind together and turn the milk into a sort of gel. The more cultures present, the faster the process goes, until they finally run out of lactose.

Step Four: Now comes the easy part. Kick back, relax, and go forget about your yogurt entirely for the next four to twelve hours. A longer fermentation time will give you a thicker, creamier, and tangier yogurt, so make it short if you're not big on sour or want something runnier. Ultimately, however, what your yogurt tastes like will depend on what culture you started with. Once it's done, take it out store it in the fridge, and enjoy! Typically, homemade yogurt without preservatives will be good in the fridge for about ten days, after which it will start tasting a bit old (But it's still safe to eat, for the most part.).

To make things a bit easier, using the new yogurt you've made, you can spoon some yogurt into and ice cube tray and freeze it for later use as a starter culture. Just make sure to thaw it out slowly before using it. Don't subject it to temperatures above 50°C (122°F) or stick it in the microwave; doing this will kill the cultures.

If you want to make things even easier, instead of using fresh milk and scalding it, you can just mix some milk powder and warm water, and poof, it's ready to culture! You should also be able to make yogurt with ultra-pasteurized milk, which is essentially pre-scalded for you. Simply put: If it has lactose, you can turn it into yogurt.

For those of you concerned about the benefits of making your own yogurt, it really is worth the trouble. For one, it's a heck of a lot cheaper than buying the stuff. Second, your own yogurt often tastes better than the storebought stuff. Third, your yogurt is guaranteed to be free of whatever you don't put in it (Preservatives and gunk like that.). Fourth, your freshly made yogurt is a great source of probiotics, typically moreso than storebought yogurt. Five, because of the good bacteria present, which feed on lactose, yogurt is almost free of the stuff, and is safe for lactose intolerant people to consume. In fact, eating yogurt regularly can even improve your lactose tolerance! And... Well... I'd say more, but I'm not advertising the stuff here, just telling you how to make it.


My yogurt is stringy, ropey, stretchy, and slimy!
Remember that you need to scald the milk; that is, keep it at near-boiling for a couple minutes. If you're using milk powder, try switching to a different brand. Some milk powders freeze-dry their milk, and so are not suitable for making yogurt. If you don't have any other choice, you could mix the milk powder with boiling water, and let it cool down to temperature. And, if all else has failed, try sterilizing the containers you're using with boiling water.

My yogurt is really runny!
There's a few things that could cause this issue. If you're using something less than 2% milk, this could be the issue. I find 3% or 4% works best. It could also be that you're not letting the yogurt culture for long enough (But don't let it sit for more than 24 hours.). If it's cold around the house, try increasing the temperature of the water bath slightly. Alternately, if you add the culture to the milk while it's above 50°C (122°F) this will kill most of the cultures, which will also result in a runny yogurt, so that's a no-no. Also, try using a culture from a thick yogurt, rather than a runny one.

My yogurt is really sour!
You probably shouldn't let it sit so long. If you like having thick, creamy yogurt, however, but hate the tanginess, you could try switching to a different starter culture. Greek yogurts tend to be tangier, so look for yogurt cultures containing acidophilus and bifidus, which help to thicken the yogurt before it reaches that sour stage. If it's still too tangy, you can try finding a culture containing L. bulgaricus, which is closer to a cheese culture than most others.

My yogurt didn't ferment at all!
If your yogurt isn't culturing and just turns into sour milk, you might want to try checking your culture. Some yogurts at the stores are pasteurized again, and so contain no live cultures. Other reasons could be that you've been adding the culture while the milk is too hot, or that your water bath and milk are simply too cold.

My yogurt is fuzzy!
Either you've somehow come across the exact culture required for Finnish viili, or you've got some serious contamination issues. THROW IT OUT. Then sterilize your equipment with boiling water.

My yogurt is all lumpy!
You probably let it ferment too long, or you used a Greek yogurt culture. It's still edible. If you want, you can mix it back together, or strain off the excess liquid with a cheesecloth and get yogurt cheese out of it.

My yogurt has separated in the fridge!
This is normal, especially if you dug a hole in your yogurt with a spoon. You can tip off the excess liquid into a cup and use it for making soup, toss the extra whey, or simply mix it back into the yogurt. Your choice. Oh, and you could probably just ignore it too. If your yogurt has completely separated, and looks like curdled milk, then you don't really have any choice but to strain the liquid off and get yogurt cheese as a result. You might also want to check that it's actually yogurt that you made, since this shouldn't happen under any normal circumstances, so try sterilizing your gear with boiling water.

My yogurt has curdled or is lumpy!
I had this one happen to me recently. If you're using a water bath as specified above, try decreasing the temperature down to about 42°C (110°F) or using less water in the bath, and see if it helps. If not, you could try decreasing the temperature lower, but I'm not sure if that would really help unless the ambient room temperature is really high. If the ambient room temperature is above body temperature (37.5°C or 98.5°F) then you probably don't need the water bath or cooler at all.

That's all, folks! If you have any queries, or run into any problems, feel free to leave a comment and I'll get back to you as soon as I can!


beechtree said...

Thanks. This is one of the best, most detailed yogurt trouble-shooting pages I've seen. Most don't mention ultra pasturized as a non-scaldimg option or the various virtues of different bacteria strains. I thought the ropyness came from not heating enough, though i'm interested to hear that there are two purposes to the scalding. I thought the bacteria did all the protien changing work.

[Demiurge] said...

No problem. I'm actually a bit behind on updates here, been busy. I have found some sites that state that UHT milk shouldn't be used for making yogurt, but so far I've had no trouble with the stuff. As for ropey yogurt, that also took me quite a while to figure out (In my particular case, it was actually that the manufacturer of the yogurt starter packs were using freeze-dried milk powder. Blech.). In most cases, though, the ropeyness is caused by not scalding the milk enough prior to use, since it's needed to denature the proteins into different forms. I don't know if overheating the milk does anything to the yogurt, since I've never really encountered the problem, but as far as I can tell it should be fine.