City Living

DIY: The Mysteries of Yogurt

Yogurt Maker

Cuisipro Donvier Electronic Yogurt Maker hide caption

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About this time last year, I started riding my bike to work every day. Then I got a basket to carry packages in. And then I brought home a Cuisipro Donvier Electronic Yogurt Maker.

My family eats approximately five or six hundred quarts of yogurt a week, between the three of us, and I'd had it with plastic tubs spilling out of the cupboard. We were going to make our own. The recipe called for starting yogurt the old-fashioned way — with more yogurt. But I quickly discovered that the stuff you buy off the shelf, even from cows that roamed free and studied Suzuki violin, doesn't always pack enough active culture to turn milk into yogurt.

We turned to off-the-shelf yogurt starter, a powder that is to yogurt what yeast is to bread. That stuff works, every time. But then came the mystery, or mysteries.

In an effort to save money, or something, I decided to try making two batches from one dose of powder. I'd make the first batch, then immediately use a bit of that yogurt — still warm from the maker — for a second batch. It should have been fresh, but it often failed. Why? Does anyone know why?

Second mystery: Lately, I've had trouble finding starter in the store, enough that I dipped into the last of the yogurt I'd made from starter and used that instead. It worked, but the yogurt wasn't as tart as I'd like. Days later, I started a batch using the not-quite-tart yogurt, and I cooked it for a looong time — maybe 15 or 16 hours. My hope was that the extra time would let the culture grow and result in tarter yogurt. It didn't. What we got was not-quite-tart yogurt that had a somewhat mealy texture. Does anyone know why? Had the milk fats begun to separate?

Third mystery: This weekend, I started a batch with the mealy, not-quite-tart yogurt and cooked it for 12.5 hours. The result was close to perfect. It's still not as tart as what you get with starter, but it's tart enough and the texture is so smooth. What went right?

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I've been making my own yogurt for close to a year now myself and I still feel like I haven't gotten the hang of it. It really does seem to be a crapshoot, but I've found that I get my best-quality results when I use starter (I order mine through Amazon, 30 envelopes at a time for about $26, so I don't feel bad about always using starter instead of starting new batches with leftover yogurt from the last batch), 2% milk and about a quarter cup of Nido, a dried whole milk that I buy in Indian and Latin markets (as opposed to the dried nonfat that's all I find in supermarkets), which adds a bit more fat and a lot more protein and therefore helps give the finished product a thicker, creamier texture.

Also, I bailed on the yogurt maker we inherited from my wife's mom, which is a pain to fill and a general annoyance to use. We gave it away and I went with the following: a basic heating pad (like the one you use when your back is sore -- in my case, it IS the one I use when my back is sore), a plastic bowl (I think it started life as a Tupperware lettuce crisper) and a large Polishware bowl that, inverted, covers the plastic bowl without touching it -- a big metal mixing bowl or stockpot would do the job as well. I put two packets of starter and half a cup of dried milk into the plastic bowl on top of the heating pad turned to high, heat two quarts of 2% milk to 110 degrees on the stove, whisk the warm milk into the powders, cover the plastic bowl with the inverted ceramic bowl, using something to prop one side of the bowl up slightly to avoid condensation dripping off the ceramic into the yogurt, which would make it watery. 12 hours later, the plastic bowl -- UNCOVERED -- goes into the fridge overnight to cool and set. One of these lasts me and my wife about a week.

Sent by Stewart | 4:14 PM | 5-5-2008

Five or six hundred...quarts? Each member of your family eats over 6 gallon per day?

What the hell, is that all you eat?

Sent by Greg | 4:31 PM | 5-5-2008

nobody has said anything about adding sugar so i hope that means you don't because sugar is one of the worst things for the human body. good luck!

Sent by jan | 4:57 PM | 5-5-2008

I can offer nothing to help but came here because I was curious to see the answers. LOL! I haven't attempted the yogurt making yet but when I do at least I know where to go to solve the mysteries!

Sent by Karen Swim | 5:01 PM | 5-5-2008

Spooky. About two and a half years ago I started riding my bike to work every day and making my own yogurt.

Yogurt culture is complicated. It's a mix of bacteria that do various things. The largest by number should be lactobacillus which eats the milk and poops out lactic acid. This gives the yogurt it's tang and lowers the pH to the point where the milk curdles and forms yogurt. From my limited knowledge I'm not sure it is possible to form the curd without a good deal of tanginess. There are other bacteria in there that are doing different things so perhaps these influence the final taste and texture. I'm not sure what temperature your machine gets to, but if it stays warm enough for long enough the yogurt can start to cook and develop a nasty, mealy texture. I've done this a couple of times by accident.

Different bacteria also work better at different temperatures. I have noticed my final product is somewhat sensitive how warm the milk was when I started and how much of the previous batch I used as a starter. I know lactobacillus is happiest around 118F, but dies at just over 120F (these numbers are from memory so don't trust them too much.) The other bacteria have different preferences. My wife likes the yogurt best when I ferment it at 109F which produces a creamier, less tangy result. The other thing that can affect the final product is the amount of bugs you start with. The smaller the bacteria count at the beginning the longer the batch will take. If you start off with too little of the old batch you run the risk of whatever bacteria came with your milk taking over and producing god-knows what. Another thing to keep in mind is that milk itself can vary from season to season and even cow to cow.

First mystery: My guess is you didn't use enough of the first batch. The yogurt should have formed eventually, but it might have taken much longer (maybe 2x to 3x) than normal. I always use one batch to start the next. I make my yogurt in a 2 quart container and dish it up with a ladle. Towards the end of the batch there is a lot of whey running around. About a cup of this is plenty of bugs for the next batch and I don't have to spend any yogurt.

Second mystery: This is why I rambled on so long. There are lots of variables. My guess is if you try to be as consistent as possible you'll be able to dial in on the result you want. One thing I remember from my beer making days is that making beer is easy. Making exactly the same beer over and over again is hard.

Third mystery: This means the mix of bugs is correct. Hmm. I wonder how consistent the yogurt making machine is. If the temperature control is erratic this could lead to unpredictable results. You can check the batch with a probe thermometer while it's cooking and find out how consistent the temperature is.

--

For any aspiring yogurt ranchers out there I highly recommend a "Brewer's Edge Digital Beer Temperature Controller." This is a nifty device that has a controller, a 110-volt plug, and temperature probe that goes into a liquid. You set the target temperature and when the temp drops too low (or too high depending on what you are trying to do) the controller energizes the plug. For yogurt I plug a heating pad into the controller and set the milk on the heating pad. For poaching I used an electric cooker. For melting chocolate I use a hot plate. For beer making I plug the fridge into the controller and flip the mode so the fridge is turned on when the temperature gets too high. This Brewer's Edge is about twice the price of a yogurt maker, but it is so much more flexible and easier to store that it is well worth the price.

Sent by Dave Wiley | 5:06 PM | 5-5-2008

I meant to add two more things.

First, the yogurt is also sensitive to the amount of protein and fat in the milk. Skim milk makes for a firmer, coarser curd than whole milk. That is to say the fat helps keep the texture loose. Adding milk powder to the batch, as Stewart recommends, adds more protein which makes for a firmer curd and perhaps a taste difference as well.

Second, if you can make yogurt, you can also make the best tasting butter you've ever had. This works better if you make your yogurt in large batches a la Stewart/Wiley, but the standard yogurt makers should suffice. Make a batch of yogurt just like you usually do except instead of milk use cream (whipping cream, heavy cream, whatever.) When done chill the mixture to refrigerator temperature. Now introduce it to your favorite appliance that beats the hell out of things. A hand mixer, stand mixer, food processor, or if you're feeling mighty, a whisk all work equally well. I use a food processor. Put the spurs to the yocream. In about 1 minute the cream will whip. In about 5 minutes the butter fat will crystallize and separate from the butter milk. Grab the newly formed butter with your hands and rinse in ice water or under cold water from the tap. Shake it dry and you're done. The final product has a delightfully tangy and almost identical to the Irish Butter you can sometimes find in import stores. Yum.

Sent by Dave Wiley | 6:30 PM | 5-5-2008

My husband and I brew our own beer so my experience with yeast is strictly of that sort but I think it sounds comparable to yogurt yeast.
Mystery 1: In agreement with Dave Wiley.

Mystery 2: If yeast gets too warm it dies. Your yeast may have partially died or went all the way to yeast heaven and gave it a weird texture. It's also possible that it cooked too long. If beer matures too long, it gets a weird aftertaste and I can imagine the same thing happening with yogurt. Also, outside bacteria can easily contaminate the yeast; in beer this also results in an even funkier aftertaste than over maturation.

Mystery 3: A fortuitous fluke? I'm guessing that there either wasn't any weird bacteria in the containers with your yogurt or there was good bacteria in there. A friend's dad who brews beer relies on leaving a little sediment at the bottom of his bottles from the previous batch and his is the best homebrew I've ever had. Yeast is a weird little organism.

Sent by Sarah Lee | 9:46 PM | 5-5-2008

This reminds me of one of my jr. high school science projects. I decided to test which way of making yogurt was better: using starter or using yogurt. If my memory serves me right, my findings supported your experience, Laura. It turned out that both were about equally unreliable in the quality of the yogurt they produced.

The downside of the science project was that I tasted *a lot* of mediocre-tasting plain yogurt for this experiment, such that years later, I still can't stomach plain yogurt or its friendly cousins like kefir. So watch out that you don't spoil your taste for plain yogurt by eating too much bad yogurt.

Sent by EBS | 1:50 AM | 5-6-2008

@Stewart and Dave: I asked and I received. Thank you. I'm impressed that y'all make your yogurt in big bowls like that. I especially like the idea of using the whey at the end to start the next batch. Dave, are you using just a regular bowl or some kind of electric thing?

Sent by Laura Conaway, NPR | 6:34 AM | 5-6-2008

@Laura Conaway: Dave, are you using just a regular bowl or some kind of electric thing?

I use a plastic, resealable container. I put the heating pad in a cardboard box, put the milk container covered with plastic wrap on top of that, and throw a blanket over the whole assembly. The yogurt is usually done by the time I get home from work. To test I just give it a shake. If it sloshes, it's still milk. If it doesn't budge, well, it's a bit over done. If it jiggles and wiggles it's just right.

Sent by Dave Wiley | 9:36 AM | 5-6-2008

Yeah, Dave pretty much nails the texture you're shooting for: think just a little less firm than Jello. I find it's important to put the yogurt in the fridge uncovered overnight because if you cover it when you first put it in, condensation from the warm yogurt will drip off the cover back into the bowl and you'll lose that good texture.

My wife usually strains her yogurt a bit, because otherwise it gets completely liquid from jostling around on her bus commute into work. I've contemplated saving the whey she drains off of hers to make homemade ricotta, but we're already having to retrain ourselves to send our kitchen scraps and coffee grounds out into the new composter in the front yard instead of down the garbage disposal, so I'm thinking one major step into Yankee Thrift at a time...

Sent by Stewart | 2:10 PM | 5-6-2008

I've returned to yogurt making, after many years away (since 1971) and am experiencing the same woes that you are. I am going to return to my old way of flash scalding the milk to kill any unwanted bacteria in the milk, liquid or dry reconstituted, keeping the lids on everything, washing everything before allowing it to touch the milk, so no skin or mouth bacteria get introduced, and floating air bacteria and yeast contamination is minimized. I produced perfect yogurt everytime, with thicker creamier yogurt produced from powdered full-fat milk from health food store or food co-op. Of course I kept the thermometer attached to the pan with the lid covering as well as possible, so I could monitor when the yogurt reached 110 degrees. Warmer temperature from the stove pilot light (covered crock on top of the stove over the pilot light) produced more tart yogurt than cooler temperatures, such as a thermos, which also took longer. Also, I am wondering if the newer antibiotics given to cows, secreted in the milk, are affecting the ability of yogurt bacteria to thrive, thus the watery products we are experiencing during these later years. Also, when I didn't use the full-fat dry milk, I used to use unpasterized milk, but don't remember if it was all natural or not, that is without antibiotics or hormones. For yogurt making, I scalded it, then waited for it to cool before adding any live culture from any off the shelf yogurt brand.

Sent by Starr | 5:43 PM | 7-27-2008