Why does soy milk curdle in coffee?


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


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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Nov 01, 2020
Add calcium carbonate to home made soy milk
by: Jacqui

Hi I'm making my own soy milk and trying to stop the curdle in coffee. I love Bonsoy, it's so good but trying to be self sufficient. I'm wondering if adding calcium carbonate to the soy milk will stop the curdles as it is used to treat heartburn so reduces acidity and is an ingredient in Bonsoy, which generally does not curdle.

Jun 28, 2020
by: Laf

I've tried most of these solutions to no avail. However if I use Alpro I don't have a problem. It tastes different and has more additives and I'll have to suck up the 100% price difference compared to the own brands and keep a carton just for my coffee.

I have yet to try the bicarb or cold pressing the coffee the night before.

Sep 05, 2019
Pre heat soy milk (slightly)
by: CoffeelovingBuddha

I found that by pre-heating (very slightly) your soy milk BEFORE adding to your morning coffee works well to avoid any curdling. I microwave my soy milk for 10 to 15 seconds before adding to my brew. Seems to work for me.

Aug 27, 2019
Milk and water first
by: Anonymous

For instant coffee I put the the water below boiling temp in cup with the soya milk, stir then add the coffee granules. Works each time. For percolated coffee I leave to cool very slightly then add milk at room temp.

Mar 13, 2018
by: Chelsea

I feel your frustration, there's nothing worse than going to make a brew in the morning when your half asleep & the milk curdles. I'm sure it's safe to drink but it doesn't look very appealing.
I'd reccomend switching to almond milk, cashew milk or rice milk. None of which curdle. If you do prefer soya, as a barrister I would reccomend heating up the soya milk first. If you don't have access to a steamer, throw it in the microwave until it's warm (not scolding hot!) & make sure the water you add is not boiling. I have noticed when I am making coffees in work that the unsweetened products don't mix as well, neither do anything that is reduced fat, or a cheaper brand.

Feb 26, 2018
READ THIS FIRST: It's all about ratio
by: Michael

I have read this blog from top to bottom with interest to see how people view this problem.

The solution has already been touched upon but I am not sure if all readers have really taken it on board (only you, the readers will know this!)

So what is going on?
Well put simply, there is something in soya milk that keeps the soya particules in suspension and there is something in coffee that causes these particles to coagulate (or flocculate I am not sure which).
Some brands of soya milk have more of the thing that keeps the particles in suspension than others and some brands of coffee (or even the strength of that day's brew!) will have more or less of the thing that causes coagulation.

So in short, you can make curdle free coffee with any soya milk/coffee combination as long as you get the ratio of soya milk to coffee ratio right. As a rule this will mean warming the milk first as the required amount of soya milk will most likely cool the drink down.

So now it is up to you to experiment with your favourite brand...

Feb 25, 2018
Problem solved
by: Anonymous

I have tried everything and came by this earlier, it is so simple and works a treat, no more curdling!!!

Jan 05, 2018
by: Anonymous

So 8ve got crohns disease and alot of bowel rem9ves. I can't tolerate fresh milk so since mov8ng to Australia have swapped to soy and now buy Bonsoy as it's non gm where as alot 9f 9ther soy is. It's been great in all my methods of coffee making then this morning decided to curdle.

Oct 06, 2017
soy milk curdle free coffee!
by: Elizabeth Amparan

Hi everyone, so what I do is bring my soy milk to a soft rolling boil. I have a hand frother; I pump that a few times to froth my soy milk and then add it to my just brewed hot coffee. No cuddles :) When I want it a little sweet, I put 1/2 teaspoon maple syrup at the end. This works for me everytime. Good luck and let me know how if this works for you. Oh, I use Alpro Original brand soy milk. Enjoy your coffee!

Jan 28, 2017
Soy milk
by: Anonymous

I think its down to the sudden temp change. So if you cool the coffee slightly before adding it, this works everytime

Jan 28, 2017
by: Anonymous

The tiniest pinch of bicarbonate of soda into the coffee before adding the soya milk. Literally a tiny pinch - just enough to neutralise the acidity slightly but not enough to affect taste. Works like a treat every time!

Jan 04, 2017
by: Anonymous

I found the same thing, I make sure I buy soya light. Also try warming the milk slightly before you pour it into your coffee and possibly a little more than you would do milk

Dec 23, 2016
by: Anonymous

Just made stove top coffee. Local grocery brand soya milk. No curdle. Exactly Same coffee in cafetiere. It curdles. With instant it doesn't curdle. Tried with other brands Alpro unsweetened doesn't curdle at all. All others curdle but only with cafetiere. Something in cafetiere coffee?

May 05, 2016
It worked.
by: Kevin

Yep. Soy milk into one mug. Made coffee in other. Poured into first mug slowly. Wallah!

Sep 29, 2015
Curdling soy
by: Anonymous

I read all your comments with interest but can add that periodic curdling happens with instant coffee too so can't be always be related to build up from pots of coffee. I have become very lactose intolerant lately and drink loads of coffee, I hate it when it curdles, so off putting. I don't like sweetened soy, coconut milk was vile, I want dairy back in my life! That said, whilst I'm not overweight and am quite fit I have noticed some weight loss/more muscle tone since I started on soy so it's not all bad plus dairy is responsible for a lot of animal suffering.

Sep 25, 2015
Bonsoy does not curdle
by: Anonymous

I use Bonsoy, and this does not curdle, and is used by many coffee shops. If in the UK, it is available in Ocado: http://ow.ly/SHVfl

Bonsoy is fairly expensive, but definitely worth it, particularly for Coffee

Jun 12, 2015
Italians never seem to have problems curdling soy
by: Jo

I live in Italy and I guess lactose intolerance is high here since many people use soy milk in their morning cappuccinos. In almost all bars I go to there is the soy option and mostly cost the same as the normal milk version. I am always noting the brand they use and I have seen all possible brands used, from expensive organic stuff to cheapo home brands. And I never had it curdle, ever. Unlike in most other European cafes where it curdles most of the time unless a specially-made-for-coffee soy milk is used. I believe the Italian secret is the temperature of the soy milk. They heat it much less than normal milk. And the sequence is the same as milk: extract the espresso, then add the foamed milk/ soy. When I make my own soy cappuccino at home, I heat the soy like normal milk, but add a dash of cold water in the coffee before I add the soy.

Jan 10, 2015
natura soy milk for coffee
by: Roger

If you're in Canada one can us soy milk from Natura

I warm the un-sweetned soy milk first (25 sec in Micro) then make K-cup or Nespresso de-caffinated coffee.

For Expresso It makes light froth but not froth like milk.

No curdle.

They do have small packaged soy milk that can be used for coffee in the office.

Nov 27, 2014
Still working on it but try this
by: Matthew from Kent

Joining the thread a bit late but here are my thoughts: my experiments seem to show that the strength of the coffee is a very contributory factor (which kind of fits in with the intriguing acidity theory - more ooffee therefore more acidity). So yes, I always heat the soya milk (my office currently has Alpro Unsweetened) in the microwave for 10 seconds and then pour the cafetiere-made coffee in afterwards. If I have put fractionally too much coffee in (tipping point seems to be 3 heaped dessert spoons for 3 people)then I pour out from the mug about 1/2 inch of the coffee and top up with boiling water. Then pour out another 1/2 inch and top up with more soya milk. Stir vigorously and this usually fixes it 90% of the time. Thanks for your comments about darker roasts which I will also now try!

Nov 08, 2014
by: Anonymous

Use soya cream. Taste awesome you only need a 1/2 a tea spoon and I have never had it curdle.

Sep 13, 2014
At Last!
by: Anonymous

Cheers, Paul - I just tried your method - and it works! No curdling. Going to experiment with different levels of coffee/water mixture as I would prefer slightly less soy milk.
Will report back - but thanks for the tip.

Sep 05, 2014
Simple solution
by: Paul

Put your coffee in a cup with any desired sweetener. Then add water up to a depth of about half an inch and stir well. Then add the soy milk to fill the rest of the cup and stir again. Finally, microwave for 1 minute 15 seconds to 1.35 depending on size of cup and then stir again. Works every time for me.

Aug 21, 2014
Curdled coffee latte
by: Mirlanx

I use non-gmo soybeans and make my own soymilk and sometimes my coffee lattes curdle. I think my coffee may be the cause. I keep a spoon in my cup for those times and stir before sipping. I usually use dark roasts but medium roast Columbian Arabic beans from Trader Joes is curdling every cup. Also, I use coconut sugar to sweeten soymilk. The coffee bean is the culprit.

Aug 09, 2014
curdles every time at home
by: Melbourne bon soy coffee

It is so frustrating! I have been trying pouring it in slow, slow and warm, slow and hot, slow and cold, and I have wasted so much time and coffee.
So I resort to going to the cafe and paying $3.50 for a mini (piccolo) strong soy cafe latte, because the buggers deliver it without splitting every time. I will work on my humility and beg them for the secret and let you know.

Jul 05, 2014
by: blackcat

I was fascinated to watch the curdling process - reminded me of the title graphics of the old Doctor Who series !!
Anyway - the way I do it - let it curdle for a few minutes - then drink the curdled part off the top - it will not hurt you - it's pure protein! Then.... enjoy the rest of your un-curdled coffee1 Cheers!

Mar 12, 2014
Simple solution
by: UCSB undergrad

Basically what is happening is that acidic conditions of the coffee are repelling the fairly non acidic soy proteins. Because of this the proteins are being pushed together and precipitating out of solution (coagulating).

Solution: Leave a spoon in with your coffee. Before you sip, stir the coffee and voila! Your coffee and soy are mixed again.

You will however need to do this before each sip if you wait more then 2 minutes between sips.

Feb 12, 2014
Hazelnut Soya
by: Sharon

I've found warming hazelnut soya in the microwave for 30 seconds before adding the coffee does the trick. Doesn't work with the Almond soya though.

Jan 28, 2014
brand schmand
by: Katie May

I use silk light. I found this thread when my soy milk curdled this morning. My coffee pot has an extra hot setting. The temperature makes the most sense. If you add more milk, and it's cold, the coffee won't have such a shocking effect on the temperature. If you add the coffee more slowly, again, the temperature of the soy milk will rise more slowly... If the soy milk is already warmed up, again, less of a drastic change.

Everything everyone said led me to the same scientific conclusion: if the temperature of the soymilk rises too quickly, it will curdle. I dumped out my cup, tried it again, slightly more milk, slightly slower pour, and voila!

Jul 28, 2013
Dark roast
by: Anonymous

When I use a dark roast, my soy milk doesn't seem to curdle.

Jul 13, 2013
Brown sugar!
by: Anonymous

For me this only happens if I put my brown sugar I to the coffee before adding my 2% milk... I've been adding it after mixing the milk in and haven't had any issues

Jul 01, 2013
Add more milk!
by: Anonymous

The more milk you add the better the result, very little curdling! And a spot of brown sugar seems to help

Mar 18, 2013
Soy Problem
by: Anonymous

I think the problem lies with the chemicals used in the processing and the pesticides that are used in the growing..Try real organic coffee, and home made organic soy milk, and see what happens..

Mar 11, 2013
In my experience
by: Michael

Just thought I'd share my experience, and annoyance, with this issue.

I've tried all different ways of preparing my coffee and with different brands of soya milk and coffee, all with varying and sometimes random results.

The best combination I've found is Alpro Soya Unsweetend Long Life milk and Percol Espresso instant coffee. It makes a perfect a brew every time. Other brands of coffee are a bit hit-or-miss. Also, In my experience, almost all soya milk is absolutely fine for making tea.

As people have mentioned, I guess it has something to do with composition of the coffee itself, such as how much acid is in it. Some of the cheaper own-brand soya milk seems to "react" with any and all coffee, and even the organic variety of Alpro Soya seems pretty useless for coffee. I have no idea why, they can't be all that different. Oat and rice milk tend to hold up a bit better, although they do still curdle with some coffee.

Jan 29, 2013
No one has the answer :o( I have some advice
by: Leanne

It’s looks as no one has the answer, it is so annoying! I am an absolute lover of coffee and when it curdles I am most disappointed!

I have found that millicano coffee is a delight with soya, also it tends to curdle the less out of most the brands. I find that shaking the soya carton vigorously and pouring it only slightly and slowly helps, hoping that the curdle particles in the carton don’t spill into the coffee….. it’s worked 9/10 times. I am presuming that the times it does curdle I am pouring to quickly.

Also, a comment before notes that using 45% soya and 55% coffee helps them. I can agree with them on this advice.

Good Luck!

Nov 21, 2012
lower ph
by: Anonymous

Try adding a pinch of baking soda to the coffee and use the coldest water you can in the coffee pot. Overheating the water and hard water cause the coffee to become acidic. The Bakingsoda softens the water.

Oct 09, 2012
It's the temperature & type of coffee
by: Laurie

As other people have noted, my experimentation has led me to believe it's got to do with the type of coffee you're using and/or the temperature of the water.

When I make ground coffee, provided I have let the coffee cool sufficiently before adding it to the soy milk, it doesn't curdle.

But every single time I make instant coffee, regardless of how long I have let the coffee cool, it curdles. So I think it may have to do with the acidity or whatever in instant coffee versus ground coffee.

Sep 20, 2012
I got it!
by: Anonymous

I think I finally figured this out. Its about porportion, how much coffee vs. how much soy milk you put in the cup. I use to put 15% soy milk, 85% coffee when i used soy milk in place of half and half and it curdled all the time, it was so annoying! I tried most of what was suggested below and none worked(although i didnt read ALL the posts) BUT what finally worked is when I put about 45% soy milk and 55% coffee, VOILA! It doesnt curdle anymore! This is why starbucks soy latte dont curdle because a shot of espresso takes up only about 15% of the cup while the rest of the cup is filled with soy milk, try it!

Sep 10, 2012
It's Not Just 'Soy' Milk...
by: Char

I found this blog out of despair. I am so sick of 'curdling' milk. I'm a lover of anything piping-hot. I've had this problem with 2% milk or sweetened condensed milk in my teas/coffee and also my powedered coffee creamers. The only thing that seems to save my coffee happens to be 'liquid'creamers (I got the powered creamer trying to cut cost...hated it anyway)I don't remember having these issues before now and I have always made my teas and coffee scalding-hot. However I will try slowly getting the milk to temp first. Hopefully this works.

Aug 24, 2012
Reasons why
by: Kasia

Years of experience:

1.Depends on type of milk (company) ,
2.coffee temperature,
3. and coffee type.
1. First of all find rather not to sweet natural soy milk. It can easly last about a week fresh in your fridge.

2.Then if you use it very cold for very hot coffee there is a big curdle risk. You can easly whipe the milk if you have espresso machine. If you just pour milk into coffee, try to do it very slowly first on spoon, spoon touching cup wall, slowly falling into coffee. You can also just wait half/one minute so the coffee temperature drops few degrees.

3. Can be very important solving your problem: Freshly grained coffee beans wont curdle, opposit to grained coffee, which you buy already grained in the shop. Even same coffee brand but from beans will make a difference. That will explain you why in the cafes of coffe companies soy milk doesnt curdle , cuz they use very fresh coffee.
Also it explains why your coffee curdle with this coffee, and the other not

...Just try one by one of this way i told you, and surly you will figure out which one works for you. SIMPLY try not to confront temperatures and make sure your coffee is fresh. good luck!

Aug 09, 2012
Curdle problem
by: Coffee geek

I have had this problem too, so after experimenting at home a bit, this is what I do to avoid it:
a) Use organic soy milk without all the additives
b) heat up the soy milk, but do not let it come to a boiling point like milk.
c) Pour in the soy milk first and then pour in the Espresso Coffee slowly, using espresso beans with nutty taste, not fresh summery taste, because these are too sour and causes the soy to curdle if that makes any sense?

Try and add comments and feedback of how you guys do it.

X Coffee geek

Jul 31, 2012
Protein powder
by: Anonymous

This was soy protein powder, not soy milk. Must be a difference to have made a bomb. I use soy milk in the blender w/ soy protein all the time but not the combo w/ hot coffee & just the powder before.

Jul 22, 2012
by: Anonymous

I used to drink black, unsweetened coffee all the time, until 6 weeks ago. I had bariatric surgery and couldn't touch black coffee afterwards so, being lactose intolerant, I started using Alpro Light. I've never had a curdling problem. I usually add percolated coffee to cold soya then nuke it in the microwave to make sure it's hot.

Jun 27, 2012
My soy protein drink BLEW UP when I added coffee!
by: Anonymous

The soy protein powder clumps, so at the gym I had a small cup of coffee staring at my protein powder in my shaker cup. I added the hot coffee, put the lid on (thinking the coffee would break up the lumpy powder before i would later add water & ice); I shook it half a shake and it BLEW up in my hand. The top one way, the bottom the other. All over the counter, mirror, gym bag & my clothes. It was a split second. Why did that happen? It was like a bomb. And, still at the bottom of the shake container (on the floor at my feet) was most of the protein powder. I can't be the only one that ever thought that coffee would help break up protein powder, can I???

May 02, 2012
Soya milk and curdling
by: John from Livingston, Scotland

OK, so that's the curdling aspect dealt with. Now, can anyone tell me why, when I use soya milk in my coffee, and no matter how long I stir it first, there is always an unpleasant residue of apparently unmelted coffee sludge at the bottom of and up the side of my cup where I have poured it into my mouth....but this does not occur with 'normal' milk ?

Apr 17, 2012
by: Jeanne

Thank you all so much. I have laughed so much at all the comments, thinking I was the only one in Montreal not able to drink my coffee without it curdling, but now I know - that we will never really know, from one brand to another, from one coffee to the next, if it will curdle or not.

What I tend to do - however, is just let it cool down, the coffee I mean, and keep stirring it , and finally, well, it does seem to un-curdle.

Apr 07, 2012
Oat milk!
by: Anonymous

I LOVE oat milk! It tastes amazing on its own and is glorious in tea. It takes a while (maybe a week) to get used to, but after that, you'll love it. I find it does seperate in coffee though, as does soya :/
Oat milk is definitely the tastiest and goes great with tea, but not coffee.
I have a coffee with me at the moment with soya milk in it, and its curdled, but meh, what can you do?

Mar 10, 2012
Curdling in Tea and Coffee
by: Dairy-Free Down-Under

Hi, just thought I'd add my 2 cents worth. I love a strong but creamy cup of Tea (preferably) or Coffee! I've recently gone totally Dairy Free, have tried Rice, Almond, Oat & Soy Milks (& creams), and have experienced the curdling dilemma with all of them, both in tea & coffee :-(

After reading all the suggestions here, I just tried heating some Almond/Cashew cream for 20 seconds in the microwave before adding it to my nice strong Tea, and it didn't curdle! So it's worth a try ...... :-)

Feb 20, 2012
Soy Milk Curdles
by: Anonymous

The coffee temp. might be the problem I use the WestSoy unsweetened and only notice the problem when I add additional coffee to my cup.

Feb 12, 2012
It's gotta be the brand
by: Anonymous

It definitely has a lot to do with the brand - almost every brand I've tried has curdled, with the exception of two: Silk soy milk (sweetened variety, in the red box) never ever curdles, and Edensoy (which I've only used once) also behaved itself. Vitasoy turns to tofu (almost) every time. Try Silk - it's fantastic.

Feb 11, 2012
Pacific Soy Barista blend avail on Amazon
by: Anonymous

Pacific Soy and Ambiance both do a barista blend, no curdling, you can order 12 packs of the Pacific Soy on amazon and enjoy perfect milk every time...

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
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.


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
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
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
by: Anonymous

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

Jun 12, 2010
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
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
by: Anonymous

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

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