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November 29, 2011 12:54 AM   Subscribe

Crockpot yogurt: I've tried this twice now, both times delicious and creamy...but the viscosity of glue. What's going on here?

I've followed the recipe that is found just about everywhere on the internet. Half-gallon whole milk, put in the crockpot on low for 3 hours. Add sweetener. Let sit covered and unplugged for 2.5. Add half-cup of (greek) yogurt, incubate for 10 hours. = delicious glue. What am I doing wrong here.

Bonus question: What's the chemistry behind this result?
posted by iamkimiam to Food & Drink (30 answers total) 27 users marked this as a favorite
 
Don't add sweetener, see what happens.

Indian style yoghurt setting has these steps (based on observing mother in kitchen) - bring milk to boil, let cool. spread existing yoghurt fully around the pot you will set it in, pour in milk, cover and set aside - no sweet stuff.

Of course with the ambient temperature difference you will need to continue your crockpot methodology. This site seems to give some common problems and their reasons and your bonus :p

Technically, Dahi is a fermented milk where part of lactose has been converted into lactic acid by the lactic bacteria.

posted by infini at 1:06 AM on November 29, 2011


Here's another site that seems to suggest perhaps you could add some powdered milk because it is what thickens the dahi/curd/yoghurt - could also be what you're using as sweetener is what's influencing the consistency?

Things that give yogurt/curd a thicker texture are -
higher level of milk fat i.e. whole milk
using dry milk powder in lieu of some of the milk, &
heating the milk longer e.g. 20 minutes vs 10 mins.

I don't personally do this, but it's one way to get a thicker texture - mix 1 teaspoon unflavored gelatin in a a few tsps of milk for 5 minutes, then into rest of warmed milk (after it is removed from stove).

I sometimes also add 2 Tbsps honey (per 4 cups, or however many ml that comes to) to make the curd less sour. It's very subtle and doesn't give it a sweet taste just blunts the sourness.

posted by infini at 1:10 AM on November 29, 2011


Er, when you say the "viscosity of glue" do you mean it's too runny, or too thick? Because I could read that either way. If it's too runny, I would try using half and half or cream instead of whole milk.
posted by Nattie at 1:32 AM on November 29, 2011 [1 favorite]


I think homemade yoghurt is pretty much always that viscosity. It might seem runny compared to supermarket yoghurts, which pretty much always have gelatine or a similar thickener added, or are strained. I like to strain my homemade yoghurt until it is more the thickness of Greek yoghurt, and then you can use the strained off liquid in bread or soups or anything that could do with a little tang.
posted by lollusc at 1:41 AM on November 29, 2011


It's neither too runny nor too thick...it's perfectly creamy. But when you run a spoon or fork through it, it has a sort of "stickyness" that is like glue rather than a "crumblyness" like, say, ricotta cheese (if we're going with two extremes here). Think mucus instead of paste.

Yum.
posted by iamkimiam at 1:43 AM on November 29, 2011


Quark is affected in a similar way by temperature in a similar way. Might be worth experimenting with lower temperatures.
posted by kjs4 at 1:47 AM on November 29, 2011


I think I'm having a little trouble understanding what you mean here, then. Crumbliness? You can put your homemade yogurt in cheesecloth and drain it. Perhaps that would give it the texture you expect?

When I've made it, whether I use Greek yogurt for starter or other yogurt, it always comes out about the same, even a bit runny, but very tasty.
posted by litlnemo at 2:53 AM on November 29, 2011


I think homemade yoghurt is pretty much always that viscosity
Not really. I make homemade yogurt and it comes out as thick as store bought greek yogurts. My method:

Microwave 1 qt milk until it's 180F
Cool to 80F
Add yogurt starter (I find it easier to use but you could use a jar of any Live & Active cultures plain yogurt from a store)
Put in yogurt maker - again, I use a Waring yogurt maker because I like the reliable results, but it's definitely not necessary!!
OR
Heat oven to 200 F, cool to 100F & put in yogurt with light on

Leave for ~16-24 hours. the longer you leave it, the more lactose the little yogurt cultures will eat up & the thicker it will be

Viola, yogurt. If it's still not thick enough, strain with cheesecloth
posted by lyra4 at 3:32 AM on November 29, 2011 [4 favorites]


Are you talking about a sort of stringiness when you dribble it from a spoon? I think those weird sticky strings are the active bacteria. In my experience leaving it in the fridge for a couple of days kills some bacteria off or calms them down or something (I don't know for sure what the chemistry is, but that's what I imagine) and in any case, the stringiness is reduced.

There are certain bought brands of yoghurt that are like that too, especially if you let them get warm again.
posted by lollusc at 3:56 AM on November 29, 2011


Yeah, it will not be the same consistency as Greek yogurt unless you drain it through cheese cloth. Using that as starter will make no difference in terms of consistency. I would also suggest waiting to add sweetener until it's done.
posted by goggie at 3:57 AM on November 29, 2011


OMG, i'm going to make a video tonight and post it here. It's plenty thick...seriously, it's thick. Imagine a giant ball of slimey snot. I could try putting snot through a cheesecloth and it would just be thicker snot. The first time I made it, it was thinner snot. I'd like not snot, thin or thick.

I like all the suggestions (thank you all!!!) and would be tempted to try them, but it's a 16 hour process that results in a LOT of product. Going into it again with some chemistry-basis for why I should add sweetener later, or keep it cooler, or microwave it first, etc. would save me loads of time and hope-filled experimentation. My housemates already think it's weird enough.
posted by iamkimiam at 4:03 AM on November 29, 2011 [1 favorite]


This is an answer to your question so I hope it doesn't get poofed but your most recent response just made me giggle because I could visualize your frustration.

What you're describing is firm not thicker - closer to caramel custard or a pudding than what the store bought foreign yoghurts are like, amirite? I googled "firm dahi" and came up with this jewel:

Before we dive into the nitty-gritties of setting yoghurt, I’m going to quickly cover what the whole process entails, from a biological point of view. The conversion of milk into yoghurt is the work of a few varieties of Lactobacillus bacteria. They basically consume the lactose (the disaccharide sugar present in milk) and convert it to protein and lactic acid. The lactic acid is what gives yoghurt its characteristic tang. I think different strands or varieties of Lactobacillus produce subtly different varieties of yoghurt. I’d recommend purchasing a small quantity from your local dairy or from a restaurant that serves fresh, nice tasting dahi on the menu, the best of which I’ve come across have been in Udipi restaurants. All you’d need to “acquire” would be about a teaspoon’s worth. I’d recommend taking a little zip-lock bag with you the next time you visit an Udipi restaurant. Bag some like you’re secretly bagging forensic evidence. Good luck with that.

I tried using commercial varieties, but I’m pretty sure they add pima and other thickening agents to it, which ends up giving you very flaccid and unhealthy looking yoghurt. The variety of Lactobacillus they use (and this I found in more than one brand) results in a terribly slimy, stringy sort of yoghurt. This happens because the bacteria (the particular variety they use) exist in long strands, or have elongated polysaccharide complexes along their outer casing.

I put about 300ml of milk to set overnight. This is how I do it:

posted by infini at 4:14 AM on November 29, 2011 [2 favorites]


I heat milk to 180F on the stove (stirring constantly), then cool it to 110F, add a little yogurt (no sweetener) and put it in mason jars wrapped in towels in the oven (turned off) overnight. In the morning, I stir it really well and stick it in the fridge. I'm sure the crockpot method is getting it to about the same temperatures. 180 is high enough to kill off any bacteria already in the milk and 110 is cool enough to let the yogurt cultures survive and start growing. They'll continue to grow until it gets too cool (I don't know what temperature that would be).

I don't measure anything and it seems to turn out fine every time - sometimes a little thin, but our family likes it that way. I can thicken it by adding a little powered milk while it's heating. I sweeten it when we eat it. Using that technique, you can make as much or as little as you want at a time - so you can experiment with small amounts until you get what you like. It only takes me about 1/2 hour of active time plus 7-9 hours overnight.
posted by Dojie at 5:05 AM on November 29, 2011 [1 favorite]


Adding sweetener early might affect the fermentation. Those guys are meant to be eating the lactose, not some other added sugar.
posted by DarkForest at 6:12 AM on November 29, 2011 [1 favorite]


Maybe what you are describing is "ropy yogurt". You might try a different starter culture, and/or make sure your temperatures are correct.
posted by DarkForest at 6:27 AM on November 29, 2011


I totally know what you mean about the glue. I've made yogurt twice (not in a crockpot), both times following exactly the same procedure (but used a different container of yogurt), and I got glue yogurt one of those times, but perfect yogurt the other time. I didn't use any sweetener either times, so I don't think that's the issue. My only guess is that it's the yogurt that you add to your milk. So maybe keep track of how old the yogurt is, and what brand you use, and see if you notice a pattern?
posted by never.was.and.never.will.be. at 6:37 AM on November 29, 2011


Imagine a giant ball of slimey snot.

Ugh, this is not what I want to imagine when I think of yogurt.

Based on your description of the problem, I'm going to suggest dropping from whole milk to 2%, and then stirring in a half cup of powdered milk right before you add the sweetener. I suspect that the milkfat is the cause of your texture issues, but lowering that will make it less thick so adding the powdered milk will add additional milk solids to compensate.

A few other questions:

What kind of milk are you using? Is it homogenized and ultra-pasteurized, like you would get in the states, or is it raw milk?

Also, check the ingredient list of your yogurt (I assume British laws require ingredient lists similar to the states). You basically only want it to list milk and active cultures, and in the states it usually lists the strain. Is there anything else? If there isn't, and the flavor is good for you, then I would say the yogurt is fine. If the yogurt has pectin or other thickeners added then I would switch to another.

Some recipes I've seen for the crockpot yogurt call for gelatin, do you use that? I wouldn't, but it is an option.
posted by I am the Walrus at 6:41 AM on November 29, 2011


You're not going to get the consistency of a Greek yogurt without either straining after fermentation, or thickening with dry milk. Each method has its merits--in the winter when I bake a lot I prefer straining, so I can use the whey in bread. In the summer when I don't have any use for the whey, I use dry milk, whisked into the liquid milk along with the starter, about a third of a cup per quart.
posted by padraigin at 6:41 AM on November 29, 2011


Bonus question: What's the chemistry behind this result?

Here is Alton Brown's show on making yogurt, go to 6:10 for his explanation.
posted by I am the Walrus at 6:46 AM on November 29, 2011 [1 favorite]


My method is similar to yours, but seems to not be "stringy" as you're describing:

1. Turn on crockpot to high (just to get it warmed up, it's going to be turned off alltogether soon).

2. Warm up milk on the stove to 180-200 degrees (kills off bacteria you don't want). You can usually tell it's ready when it starts to look frothy. Don't let it burn.

3. Set the pot in the sink with cold water to cool it to 90-110 degrees (sets up the right temp for your good bacteria). Usually takes about 10 minutes.

4. While this is cooling turn off and unplug the crockpot.

5. I mix about 2 Tbs of yogurt with live culture per 4 cups of milk prepared with a bit of the warm milk then dump it all together in the crockpot and stir.

6. Cover the crockpot, wrap it with a towel to keep it warm and leave it for about 10 or so hours.

7. Once that's done, transfer the whole thing to the fridge, but don't dig into it until it's had a chance to cool down. That last step seems to let it set up and be a little firmer/creamier than if you eat it right away. I add sweetener and other stuff as I eat it rather than in the big batch because I'm not sure how the other sugars would affect the bacteria.
posted by goggie at 6:49 AM on November 29, 2011 [2 favorites]


I've made my own yogurt for a long time, using a bit of each batch as a starter for the next batch. I have gotten ropy yogurt, and once the culture went ropy, it tended to get ropier and ropier until I just gave up and used a new starter. I'd assumed that a new organism got introduced to my culture. In some parts of the world, this is considered a desirable texture, actually.

Some claim that texture comes from certain strains of bacteria, which exude polysaccharides, while some say that it can simply be caused by an excess of L. acidophilus over L. bulgaricus (typically the two most important bacteria strains in a yogurt culture.)

I'd recommend trying a different culture. I've always had good luck with Dannon All Natural. I'd definitely look for yogurt whose only ingredients are milk and bacteria.
posted by BrashTech at 7:27 AM on November 29, 2011


I was experimenting with different varieties of milk fermentation, and my yoghurt turned out semi-solid like some kinds of store-bought yoghurt (or ricotta cheese), though a bit thinner. On the other hand, when I was trying out kefir as a starter, which seems to have some kind of fungus in it in addition to the lactobacillus, it had the consistency you are describing.
So, one more vote for consistency depending on the kind of microbial culture you put in.
(I used homogenized, pasteurized, low-fat milk.)
posted by small muffin collider at 7:32 AM on November 29, 2011


I am also a little confused. When I buy greek style yogurt at the store, it is usually the consistency of store bought sour cream. Which is to say, sightly gelatinous. Stir it up and it gets creamy. What happens if you stir up up really good?

If you want paste, you need to drain off some of the whey. This isn't running it *through* cheesecloth, but putting it into a cheese cloth and letting the whey drip out. Your yogurt stays in the cheese cloth. And I think the other poster is right, if you want it to be a little less creamy and more pastey, use milk with less milkfat. But I think the first thing to try is stirring it up really good to homogenize it, and then drain off some whey.

And yeah, don't sweeten until you are going to eat it- regular sugars in there can allow any stray yeasts to start doing their yeast thing. The sugar might also interfere with the lactobacillus doing their thing.

The science is that the lactobacillus eat the lactose and poop out lactic acid. The lactic acid curdles the proteins. Instead of homogenous strings of protein molecules, they curl up into little balls. Think of it like a very fine powder mixed with water.
posted by gjc at 7:36 AM on November 29, 2011


gjc: "I am also a little confused. When I buy greek style yogurt at the store, it is usually the consistency of store bought sour cream. Which is to say, sightly gelatinous. Stir it up and it gets creamy. What happens if you stir up up really good?
...
The lactic acid curdles the proteins. Instead of homogenous strings of protein molecules, they curl up into little balls.
"

The curling up into little balls is correct, that is how the proteins coagulate. When you stir it, you are basically unwinding the balls of protein, which is why the yogurt gets a looser texture. As it sits they recoagulate (wind up again) and the texture firms. Although during this process some of the whey comes out, which is why you sometimes find watery liquid with your opened sour cream or yogurt.
posted by I am the Walrus at 8:02 AM on November 29, 2011


2. Warm up milk on the stove to 180-200 degrees (kills off bacteria you don't want). You can usually tell it's ready when it starts to look frothy. Don't let it burn.


That may happen, but that's not the real reason why you need heat milk to 180F before you make yogurt. The reason why you heat it first is to "break down" some of the protein in the milk so that it thickens better. It's a chemical process you need to initiate to change the structure of the milk so that the yogurt gels properly. Quora has a decent thread on this:

When making yogurt with pasteurized milk, why must the milk be heated to 180 degrees and then cooled again?

And Chowhound:

Is "scalding" or heating milk really that necessary for making yogurt?

If the OP is not heating to > 180 F first, that's going to be one of the biggest problems causing the "glue" texture- sorry I missed the detail the first time around.
posted by lyra4 at 9:07 AM on November 29, 2011 [2 favorites]


I came in here to say what lyra4 just said. Scalding the milk denatures some of the proteins to allow proper thickening. If you don't do this, your yogurt will be less thick. You could do this in you crock pot, but it will likely take forever. I recommend a large pot inside another pot full of boiling water.

Also, don't add any sweetener until just before you eat the yogurt (possibly you are encouraging a ropy culture). Use Balkan-style yogurt as a starter if you want Balkan-style yogurt (look for a yogurt that is sufficiently thick without including thickening agents - if it worked once, it can work again for you, while if they had to add thickening agents, the culture may not be up to the task).

Finally, it pays to better monitor temperature. Crock pots vary, so who knows what temperature you are incubating at. Use a thermometer! I have good results incubating around 45C for 4 hours, but there is a fairly wide range of temperatures that you can use.
posted by ssg at 9:52 AM on November 29, 2011


Keep in mind too that store-bought yogurt has often had its texture artificially altered. For example, I just grabbed a cup of Lucerne Light Yogurt from my fridge. In addition to everything else, it includes tapioca starch, corn starch, and kosher gelatin - three things intended to change the texture.

You should at least be able to get something less repellent if you follow all the great tips here, though!
posted by ErikaB at 11:13 AM on November 29, 2011


lyra4, THANK YOU. You have solved the mystery of why sometimes my yogurt is lovely and thick, and sometimes the consistency or half and half. I bet it's because I didn't heat it quite enough. This is awesome-- I quit making yogurt when I got so super frustrated with inconsistent results.

I actually have one follow-up question for the yogurt masters here. Sometimes I make yogurt in he crock pot, sometimes in sealed mason jars wrapped in towels in a cooler, and sometimes open mason jars sitting in warm water (e.g., in a warm water bath). It seems like I don't have luck with sealed jars-- the yogurt is more likely to be runny. Does the bacteria need oxygen (with a closed crockpot letting just enough in)? Or is it just coincidence? (Yeah, I should read the whole science article linked, as soon as I'm off my phone.)
posted by instamatic at 2:50 PM on November 29, 2011


Glad that the "heat it above 180F" first step is helping.

I do mine in open jars inside the yogurt maker. Then the machine has a lid that goes over the top. My yogurt cultures for over 18 hours, and I always find at the end of that time that the yogurt maker lid has a lot of condensation on it. So maybe you could improvise something similar like if you culture in a cooler leave lids off the individual jars but cover the cooler itself?

Clearly the yogurt maker is not necessary if you have a reliable way to regulate the temperature for 18 hours. Oven with the light on is the one I hear works the best. But I eat at least a cup of it every day and so the $70 for a yogurt maker a few years back has more than paid me back in not getting bad batches and wasting milk (or buying expensive yogurts with extra crap added in). YMMV obviously, but for me it has worked out to be a good investment.

Anyone else making yogurt with non-homogenized milk? I am getting addicted to home made cream top yogurt. It's awesome.
posted by lyra4 at 6:14 PM on November 29, 2011


Yesterday I attempted it again, taking into account all of the suggestions above, and...total success! This time I made sure that I scalded the milk good and proper (still using whole milk though), I didn't add sweetener, and I switched yogurt brands to something non-greek. It was so simple and it turned out fab.

One thing I noticed as I poured the yogurt into a big jar...this batch "plopped" into the jar, like yogurt. The previous batches streamed in like ropes of melted cheese (or glue). This is so much improved. Thank you all for your help!
posted by iamkimiam at 3:49 PM on December 10, 2011


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