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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?

Click here to add your own comments

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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