Ask the Alchemist #183

Level: Apprentice

Reading time: 8 minutes

I have been making a batch of chocolate, but I am unable to lower the acidity taste (vinegar like) that i sense on my chocolate. i have been trying to find a solution, and nothing so far. Maybe you can help me lower that acidity taste I have. The mix is 65% cocoa and 35% sugar so far and no powdered milk.


This is tough to answer without tasting the chocolate.  Near impossible really.  But of course I’m going to try.

Vinegar is acetic acid and is a natural by-product of the fermentation process of cocoa beans.  My storage facility smells very strongly of acetic acid. This surprises many visitors as they assume it will smell of chocolate.

Acetic acid is pretty easily driven off in the roasting process.  Pure acidic acid boils at 244.6 F.  I’d like to say all you have to do is make sure your beans are above that temperature and your issue is taken care of, but it isn’t quite that simple.  But it isn’t that far off either.

There is moisture in cocoa beans.  If you stick your hand near the outlet of your oven or roaster you will feel the water coming off the beans.  And it is carrying other compounds with it.  One of the neat things about boiling points and chemistry are all the interactions.  As I showed in making honey chocolate, where ethanol pulls water out of chocolate below 212 F, water also drags acetic acid out of the beans below 244.6 F.  It isn’t quite as strong of an effect because water and acidic acid don’t form what is called an azeotrope,  or mixture that can’t be separated but it does a pretty good job.

You can smell the acidic acid coming off well below 244.6 F.  Often 215-220 F.  But the hotter you go, the more that will come off.  And also the longer you are at an effective temperature, the more that will be driven off.

A practical consideration of this is slowing your roast down near the end and giving the beans time to soak in the heat and time for the acetic acid to rise to the surface and evaporate.  Remember, just because the surface of the bean is 250 F does not mean the interior is.  And unless you have hung out at 250F for 10-15 minutes (not what I am suggesting) than the interior simply won’t be at that temperature.

So that is the first bit of advice.  Make sure you are roasting fully enough.  If you have a thing for light roasted chocolate but don’t like acidity pick a bean that is a bit lower in acetic acid to start with.  You don’t have to remove what isn’t there in the first place.  And even if you do like it roasted lighter, it doesn’t mean you can’t get rid of it.  Just extend your roast a bit.  Maybe you will have to go outside the standard suggestions and really stretch it out.  I don’t have concrete examples of this because mostly the resulting chocolates are not to my taste.

Regardless, you have roasted as you like or missed the roast you wanted and have beans with a bit more vinegar than you like.  All is not lost.  There is quite a bit you can do while the chocolate is refining in the melanger.

Just by the natural process of grinding and aerating a lot of volatiles (acetic acid included) will be driven off.  If you can raise the temperature a little it will help.  Point a heat lamp on it.  Put the whole melanger in an open top box (the motor heat will warm it – but leave the box open or you can burn out the motor).  Over the 24-48 hours that little extra heat will help drive off the undesirables.  Adding a fan to blow gently over the top of the chocolate can also do wonders.

But be warned, all things come at a price.  You don’t like acetic acid because it is strongly flavored.  And you are doing stuff to drive off the strong flavors.  But you want some strong flavors in your chocolate most likely.  And some of those other compounds ARE going to come off at the same time.  It’s a matter of balance.  When has enough acetic acid come off but not some of the key fruit esters.  Note I say ‘raise the temperature a little’ and ‘blow gently’.  Balance my friend.  Balance.   Too much heat and air and you can make neat brown stuff without much flavor at all.

And if that doesn’t do the trick?

Well, you mentioned milk.  That can and does do wonders.  Madagascar, one of the most acidic beans out there, is not often one of my favorites (I’m a deep brooding kind of chocolate guy) but on the flip side some amazing chemistry and alchemy happen when you add milk powder.  The acids are not just hidden, but converted.  And converted into lovely flavorful compounds.  You don’t necessarily have to make a milk chocolate per se.  2-3% milk powder could well do the trick without turning it into what you think of as milk chocolate.

Finally, and I’ve had this happen more than once when troubleshooting this issue in person, it may simply be that you are misinterpreting another flavor in the chocolate for acetic acid because it is what you are familiar with.  And in cases like this, there is often nothing to be done to ‘fix’ the problem as there is no problem.  It‘s is simply that you don’t like the flavor of a certain bean.  Keep that option open.

To summarize,

  • Make sure you roast fully and if you are roasting low, then roast longer.  260 F is good and safe.
  • Refine at a little higher of a temperature.  135-145 F.
  • Blow a gentle stream of air over the chocolate (and taste often)
  • Try adding a little milk powder. 2-3%.
  • Consider that you don’t like a given bean and move on.

And above all, have fun.

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