Why does soy milk curdle in coffee?

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Why does soy milk curdle in coffee?

QUESTION:

Why does soy milk sometimes curdle in coffee, and how can the curdling be avoided?

ANSWER:

Great question. I’m sensitive to lactose myself and generally use a lactose-free cream or milk. But from time to time I have tried a soy product.

I had the same problem as you. The weird part is that soy milk curdles in coffee sometimes, but not always.

The curdling occurs when the acid in the coffee coagulates the proteins in the soy milk. Instant tofu!

How to avoid it? Tough question. Curdling seems to be a triggered by a variety of factors, including the brand of the soy milk, the heat of the coffee, the acidity of the coffee and even the speed with which the soy milk is added.

Looking through other people’s experience with the curdling soy problem, here are a few tips you can try.

1. Shake your soy milk thoroughly before pouring.

2. Pour the soy milk into your cup or mug first.

3. Then pour in the coffee, slowly.

I’m hoping others contribute to this thread so we can get some more definitive answers...if there are any!

Comments for
Why does soy milk curdle in coffee?

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Jan 19, 2012

heat the soy milk first
by: jyanzi

i heat the soy milk in the microwave oven and foam it before i pour coffee over. no problem here.

Dec 15, 2011

My solution
by: Chris

I'm sure it is the acid in coffee that causes curdling. I tried adding a tiny amount (about half a pinch!) of bicarbonate of soda/baking soda to the mug before adding the water. It fizzes like cola for a few seconds,but the soy milk but tastes the same to me and it never curdles!

Oct 16, 2011

Maybe, possibly . . .
by: Tish

Layin in bed wondering if today will be a good coffee day or another frustrating pour it down the sink day, when I found this thread. Happy to discover it's not just me! I have tried every variable in the assembly of what I hope will be a simple uncurdled soy latte - I'm becoming downright superstitious! Somedays a certain 'trick' works, and others . . . gahhhh!
So while I read, I'm figuring out that there may be no solution - and the thought keeps nagging - so why was my soy latte when purchased from Starbucks NEVER CURDLED??
Then, halfway through the thread, yet another mystery nagging my quest for the perfect soy latte came to mind - yeah, why does Starbucks insist on using VANILLA soy milk?!!!
Huh? Could it be . . . VANILLA??!
I aim to find out - right now!

Oct 06, 2011

Rice Dream and soft water
by: Heidi -Hi

Don't know about soya milk but have used Rice Dream for years. When we lived in a hard water area - Kent - it often curdled in hot drinks. The same in Norfolk - hard water. After we moved to Cornwall - no problem - soft water - the same when visiting Manchester - soft again. We get over the problem by using filtered water in hard water area - or carry Cornish water with us for visits! Hope this helps someone! Having said this - in the last few weeks we've found even Cornish water is curdling after 3 years with never a problem?

Oct 04, 2011

it's not consistent!
by: Anonymous

I drink Decaf Starbucks Via (no coffee shop anywhere near my office) and I often have to use powder creamer. This curdles too!! I think it's about the temperature of the coffee. If I mix the instant coffee and the powdered milk and sugar, then add a little water, it's fine. I add more and more water and it's still fine until I reach near the top of the cup. Then it's instantly and pervasively curdled. I had no idea that would happen with non-dairy creamer. It works for me to mix the creamer and some water, add the coffee, then fill up with hot water till about 3/4 of a cup. Better than drinking a cup of what looks like miso soup.

Aug 18, 2011

Cold coffee & soy
by: Sarah-san

I only noticed it when I made iced coffee with instant Nescafe coffee powder... it doesn't seem to do it when I make it with hot coffee. For me, the separation doesn't seem to affect the taste, so I wouldn't worry about it.

The reason I use soy milk is because of what they do to milk cows... it's really horrible. They keep them pregnant all the time, and don't let them go outside. What kind of a life is that? Soy milk is much better for your health and your karma. :)

May 05, 2011

Rice milk in tea...
by: Anonymous

I have recently had to give up 'dairy' and am putting Rice milk in my tea - it looks horrid!!!! I've tried every variation - milk first, tea first etc. but it still curdles! My remedy is to leave the spoon in the cup and just stir before every sip!!! Not particularly comfy!!!! ~sigh~

Apr 15, 2011

acidy (heavy or non fresh anymore) filter coffee
by: Anonymous

Ok I have to add on my Acidity comment that today I bought an Americano coffee in apostrophe central London with Soya hot milk and the milk curdle inside the coffee (damn....I thought acidity due to lack of freshness was the reason but ....I guess not just).

Still havent figured it out but have to admit that coffee in apostrophe (three shots of espresso and then water) is quite strong.

Additionally its quite tripy to look at the milk as it moves into the coffee.....I might make a video and put it on you tube at least to enjoy the visual effect that coffee and hot soya has to offer....

Apr 11, 2011

acidy (heavy or non fresh anymore) filter coffee
by: London Starbucks Filter cofee drinker

My answer is for Hot soy-or soya- milk and Starbucks filter coffee (pike place, house blend, Colombian and until recently which now stopped the "estima"). Please don't tell me that is shitty coffee I know. But for 1.20£ here in London including soya milk plus hours of non interruption with my laptop......etc its a steal.

Among other answers (put soy first and then coffee, or shake the box before use, or steam it hot) I think the main reason for me is coffee that stays longer than an hour in the cafetierre tank (filter coffee that is) and becomes ACIDY.
Never happen when I get Americano with hot soy. Let me also say this: I knew this girl she was working at a Starbucks in Las Vegas and she told me that they add artificial cafeine into the coffee. I am saying that as a possibility that this is the reason the milk gets curdle as the coffee is very strong. ......anyone else heard about artificial caffeine into the Starbucks coffee ?

Mar 30, 2011

Acidity
by: Kai

I wonder if it's all just the acidity vs the quantity of milk. When I'm intentionally curdling real milk (to make cheese) by adding acid over heat, I find I have the best results if I have the highest acid to milk ratio - i.e. 1 litre of milk and concentrated citric acid powder is sensationally fast, whereas 2 litres of milk and lemon juice may not even curdle completely.

So for soya vs coffee, as I sit here with a curdled cup despite heating the milk and adding the hot water extremely slowly (now stiring it before every sip so I can trick myself it's not yukky!), I will next be trying half a spoonful of coffee with twice as much soya.

Or perhaps a more refined experiment will be to boil water, add cold soya milk to it and check it doesn't curdle (which I expect it would not), and then add instant coffee slowly to that, and see whether it curdles and at what amount of coffee it curdles at.

My colleague would like to be acknowledged as the provider of soya milk for my experiments.

Mar 29, 2011

Coconut Milk!
by: Loparna

I have just been using SO Delicious coconut milk, and it's delicious. My non-lactose intolerant girlfriend even agrees it tastes just like milk in coffee. Nice and fatty.

I've tried just about every other trick discussed here, but they only work sometimes at best. There is an element of black magic to this phenomenon.

Enjoy!

Mar 21, 2011

Hot drinks
by: Anonymous

I work as a barista at a local vegan-friendly coffee shop. Customers have a problem with "milks" and real milks curdling in any high-coffee-content drink when they add it themselves.
I've found that the biggest factor with that is the heat of the milk when added. I find that steaming the milk/soymilk/creamer for just a bit helps tremendously - I've never had it curdle this way.

I don't have a solution for cold coffee as of yet, though. I think that's all up to the acidity levels of the coffee.

Feb 26, 2011

For Cafe owners
by: Marty

Vitasoy also make a soy milk specifically for coffe, but unfortunatley it is only available to coffe shops" "Go figure" check it out on there website

Feb 26, 2011

This works really well
by: Marty

I have just started on the soy, not by choice!!
What I do is use vitasoy high fibre and put it in a
Nespresso aerochino machine which heats and whisks, it comes out awesome really thick microfoam, no separation here, If you want it a bit hotter I put it in the microwave for 15 secs.

Once you try This you'll use it everytime

Feb 24, 2011

almond milk
by: Anonymous

I have found that almond milk does curdle in acidic coffee as well...

Feb 14, 2011

it worked!
by: posey plum

Added coffee slowly to the soya milk and it worked a treat - no curdle at all - very smooth.

Jan 17, 2011

no more curdling soymilk
by: Anonymous

I have totally eliminated curdling soy milk by heating the soy milk to the same temperature of the coffee (about 30 seconds in the micro). Continuously stir as you add the soy mijk to your coffee. No more ruined coffee!!

Jan 17, 2011

why does soy milk separate in coffee?
by: Anonymous

I love soy lattes, have made them for years, and still can't understand why they sometimes separate! I grind fresh dark coffee beans before making it in my stovetop espresso pot; then I shake the soy milk carton and pour it into a pan to heat on the stovetop, whipping it with a spiral wire whisk. Soon as the coffee is done, I pour it into the hot soy milk. Sometimes it curdles. My only variables are how recently the carton of soy milk was opened, how hot the milk gets, or how much I whisk it.

Dec 15, 2010

Rice Milk!
by: Mark van Wyk

Rice Milk does not curdle in coffee. If you mix 2 teaspoons of rice milk with a cup of hot water (in a separate mug), and give it a good stir, you'll have AWESOME milk.

Pour that into your coffee, and you have solid cup of coffee (no curdling).

I much, much prefer Rice Milk to Soya Milk.

Nov 27, 2010

not the brands
by: Curdle Hurdle

I make stove top coffee almost every day using the same soy milk (bonsoy) and the same coffee for at least the time that the bag lasts. Sometimes I heat the milk, sometimes I don't and nearly every time it's all fine. Just every now and then I get a cup which will curdle and even when I make a new pot it will curdle again. This is why I think the residue theory is at play.

The same when I use the espresso machine at work. They use vitasoy and I assume they just get the same beans every time. It's only been once or twice that it curdled there but it does happen randomly. So I usually clean the machine a bit more thoroughly and it seems to work.

Anyway, that's my experience.

Nov 23, 2010

Didn't work for me
by: Anonymous

I heated up the soy milk almost to a boil, added it to coffee made in a french press (you need to let it stand for a few minutes)so it is not that hot anymore.
It did curdle a little less but it did curdle, not very tasty looking. I think it is the brand of soy.
I used to use only one brand of Decafe coffee but sometimes changed the soy milk and it happened.
So IMO for me it was the change of soy milk.
It never happened with my own home made soy and it never happened with hot cocoa or chocolate pudding that I made last night.
Curiouser and curiouser. Coffee mate!!

BTW, I tried that Keurig coffee this weekend, wow great coffee but a tad too expensive for me, the once in awhile coffee drinker.

Nov 23, 2010

Mine curdles too
by: Anonymous

In my case I think it was the coffee and maybe the brand of soy milk, this is my first time using both. I have not made coffee for almost 2 years just started to get a yen for it.
The coffee was WaWa and and the soy was Vita Soy.
I let the second cup cool a bit and it still curdled but not that much.
I am going to try again, I want my coffee. Maybe I will go back to coffee mate.

Nov 20, 2010

A theory
by: Curdle Hurdle

I had a theory that maybe the residue of old coffee in a coffee pot or machine might make the curdle happen. I made a stove-top pot of coffee, poured 3 cups into heated soy. The first two were fine and the third curdled. So I tried a new batch. Still curdled. Guess that third cup just had a curdle curse. Maybe this coffee I bought is particularly acidic. I have had the experience though that the milk curdled, then I cleaned the machine or the pot a bit better and the next cup was fine. Could that be a clue?

Nov 19, 2010

Thanks for the tips
by: SoyaMia

I have noticed that the soy milk curdles sometimes and the previous posts make a lot of sense. I will try pouring hot coffee slowly into soy milk. This got me thinking that milk can be brought almost to a boil slowly without curdling.

Nov 18, 2010

fabulous!
by: NZGirl

this is awesome! So many answers! Next cup i make, I'll be trialling some of these methods! Thanks

Nov 12, 2010

? lactose intolerant
by: Anonymous

Trialling soy milk and have had issues with soy curdling. Will trial the ideas

Nov 10, 2010

Curdling Soya
by: Anonymous

I have found that, having made a cup of coffee (instant) if a wait a few moments or, give the drink a few stirs to take it off the boil. The soya milk is less likely to curdle.
However, I will have a go at pouring in the milk first (as I do with drinking chocolate) and see what happens. "Bootneck"

Nov 08, 2010

coffee tempature...
by: Anonymous

I found if I heat my milk first then add hot coffee it works fine, if I add milk and coffe and then microwave, curdle and hot coffee and cold milk, curdle.

Oct 30, 2010

just made a cup with strawbery soy milk
by: Anonymous

It worked perfectly....slowly is the key, didn't curdle.

Oct 25, 2010

Curdling Soy Beverage
by: David

My experience as well. Just tried the soy in the cup first, coffee added slowly second. Worked great. I think the slowly is significant.

In chemistry we add strong acid to water not water to strong acid. Perhaps for a different reason because the heat of solution of the water/acid mixture will cause the water going into the acid to heat rapidly and spit or boil, if you will, splattering small acid droplettes. Hence the general practice of using shields and wearing appropriate protective wear.

Great coffee.

Oct 21, 2010

only once
by: LB

same here... i warmed the soy first and added the coffee... still curdled. I have tried it all different ways and once, only once it didn;t curdle and it was a wonderful cup of coffee... but why?? I don't remember anything I did differently - have waisted lots of coffee and soya so far.

Sep 17, 2010

Soy milk vs. soy creamer
by: Anonymous

My coffee quandary: I heat up my soy creamer, then let the Tassimo machine add a shot of espresso. No curdling. I heat up regular soy milk, then let the Tassimo machine add a shot of coffee. Curdling. What is different about soy creamer that makes it non-curdling?

Sep 13, 2010

Kenco!?!?!?
by: Anonymous

Instant coffee doesn't count as coffee.
I make coffee 2-3 times a day in soy(a)milk. steaming the milk properly and using freshly roasted and ground coffee never curdles coffee (minimum of freshly ground). It's always instant and pre-ground coffee that has too much acidity and will curdle the coffee. If that is all you have to work with, then getting the temperature right will stop curdling sometimes. I suspect what happens in this case is it only curdles some of the soymilk before the acid is neautralised.

Aug 05, 2010

Coffee and soya milk
by: Sandra

If the soya milk is heated and then added to the coffee and water no curdling takes place. Works every time.

Jul 24, 2010

Soya milk and coffee
by: Sharyn

Jarrah brand has never curdled on me and I drink at least three cups a day.

Jul 04, 2010

Acid
by: Anonymous

Acid, heat together curdle soymilk. If the coffee roast is light it will be more acid

Jun 12, 2010

mugs?
by: Anonymous

This curdling thing happened to me this morning but the odd thing was that I made two cups of coffee, one in a commuter mug and one in a regular mug. The soy milk only curdled in the commuter mug. Maybe it's because the coffee was hoter in the insulated commmuter mug?

May 25, 2010

it's the acidity
by: bucookie

It's the acidity. Yes the temp of the coffee comes into play, but the acidity is what has always been a problem for me.

It's definately not the quality of the coffee. A nicely light roasted quality coffee will be more acidic due the light roasting. I'm not sure what Kenco coffee is, or the others mentioned, but it sounds like some "off the shelf" brand. If that's the case, temp is your issue. Heat your milk, shake it first, stir as it goes in...all those should work.

To the person who suggested bicarbonate...does it change the taste at all? I guess I'll have to try it and find out.

Also, there are barista soy milks out there that are designed to handle the temp of foaming and will work better with coffee. Pacific makes one I believe it's called a soy blender.

Apr 30, 2010

It's the coffee not the soy milk
by: Anonymous

If the coffee is too acid then you will get curdling no matter which soy milk you use. Use a better quality coffee and you won't have any problems :)

Mar 27, 2010

milk then coffee not presentable.
by: AnonymousNo.52 :B

i work in a small cafe and i get a few soy coffees every day. And its horrible to see it turn to mush as soon as the milk is added. when i do my flat whites, i like to have the thin layer of creama along the top of the coffee in the cup, then add the milk in so i can do my designs on the top and make it presentable. some have suggested adding the milk first then the coffee, but this doesnt help me. by doing it this way, it makes an untidy coffe which i have to take out to a paying customer, not a fun experience to undertake as i found out. i've tried keeping the temperature of the soy milk lower to stop it curdling but this doesn't seem to help either - and i get complaints of not hot enough coffees. is there any other way of stopping this from happening? thanks in advance. :D

Mar 22, 2010

teaspoon
by: Anonymous

I always keep a teaspoon in the mug so I can keep stirring it, LOL, sorry, not much help ;-)

Mar 17, 2010

have to heat the soy milk first
by: Jen

I tried Sibo's suggestion. It works! Just put a little soy milk in a separate cup and microwave it for 30 seconds first. Then add it to the coffee. Just like Starbucks, where they steam the milk, then add it and you never get it curdled. ;).

Feb 13, 2010

it's pretty simple
by: RA

Put the soy milk in the mug first, then add the coffee.
I only get curdling if I add soy milk to a mug already containing coffee.

Feb 12, 2010

Thanks for the tips !
by: Anonymous

Hi All, I`m just opening a vegetarian cafe and this info is invaluable for me as i`m sure i`ll get vegan customers too !

:)

Feb 03, 2010

Weaker Coffee
by: Tracy

Hello, I find that if you take weaker coffee that it doesn't curdle so much, I like to shake the soy so that it goes all frothy on the top of the coffee :)

Jan 24, 2010

Soy alternatives?
by: CoffeeBabe

Has anyone tried rice, almond or oat milk as an alternative to soy in coffee? I've had the same curdling problem when I've used soy, so I'm excited to try some of your ideas. If anyone's tried an alternative to soy in their coffee, please let me know what you think.

Jan 17, 2010

100% successful ! even with decaf coffee.
by: Anonymous

I read and tried so many ways making coffee with soya milk but I found out this is the BEST & Easiest way - just shake the milk before pouring into cup, then add the coffee in...voila !!! I LOVE my coffee now ..huraaaa....

Nov 09, 2009

Microwave it
by: Shibo

I've learned to microwave the soymilk in your coffee mug for 30 seconds before adding the coffee.

Oct 29, 2009

soya goes in first
by: Oliver Scott

I had this frustrating problem until I found out that to avoid it you have to put the soya milk in the cup and pour the coffee on top. Been working for me so far.

Sep 02, 2009

How to avoid curdling...
by: Adam Pritchard

An asian girl taught me a method to pour soya milk into coffee without curdling it.

Take a teaspoon and cool it under the cold water tap. Place the teaspoon on the surface of the coffee and angle it slightly. Now pour the soya milk slowly onto the teaspoon and watch the soya spill slowly onto the surface of the coffee....

This should prevent it from curdling, don't ask me how this works, but I've just done it and it works :-)

Aug 20, 2009

Thank you
by: Anonymous

I never thought I'd find so many great answers, thank you everyone for your insights, please continue to post!

Jul 27, 2009

no more curdled milk
by: james

put the soya milk in then the hot water mix then add the coffee it works every time

Jul 26, 2009

problem solved
by: Anonymous

ok. been vegan long enough to have this sussed. make the coffee black and stir. then add a pinch (not much at all) bicarbonate of soda to kill off the excessive acidity in the coffee. you'll see it fizz a little. stir again. then add the soya milk. problem solved. you're welcome x

Jun 22, 2009

Soya milk
by: Anonymous

I use Kenco coffee and have tried several different soya milks (unsweetened)all seemed to curdle except Morrison's which was ok until they recently (I assume) changed suppliers as their's now curdles as well.
Is it ok to drink like this as it tastes ok? just doesn't look very nice.

Feb 11, 2009

Kenco
by: Anonymous

I have found that Kenco does not make the milk curdle when using soya milk.

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Why does soy milk curdle in coffee?

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Why does soy milk curdle in coffee?