Ask the Alchemist #161

Level: Apprentice

Read time: 7 minutes

I have been making a batch of chocolate over and over.  It is sharp and astringent.  I think I keep over roasting it but nothing works.  I have tried roasting from 250 to 300 degrees for 15-30 minutes.  What am I doing wrong?


Somewhere along the line the trend has been to roast cocoa lighter and lighter for fears of not over roasting it.  That is an admirable goal.  You don’t want to over roast your cocoa.  Unfortunately this is the classic result that I am seeing every single week.  Effectively under roasted beans or possibly even raw beans that are sharp, astringent and lacking in chocolate flavor.

Before we going any further, I want to define who I am talking to.  If you like your chocolate and how you are roasting, then this article isn’t aimed at you.

If there is that little voice in the back of your head wondering why you chocolate isn’t quite right and you are fearful of over roasting because all the experts (self proclaimed?)  out there who have never roasted a cocoa bean in their life warn against over roasting, then maybe you should read on.

I’ve tried to over roast.  It is REALLY hard.  I’m talking  you have to try to over roast and you still might fail.  I’m not joking here.  I am kind of dumbfounded where the idea came from that it is easy to over roast cocoa let alone that it burns easily.

Let’s talk about roasting.  As in really what is happening.  To do that I need you to put away what you think you know about roasting cocoa and instead engage what you know about cooking and baking in general.  Because the rules are the same.  There is nothing special or magic about roasting cocoa beans.

Ok.  Agreed?  Great, let’s begin.

What has to happen when you roast?  You need to take a cocoa bean that is around 70 F and take the whole thing, all the way to the center, to somewhere in the range of 230 to 260 F.  From experience, I have learned that I personally like it best when that can happen in 15-30 minutes.  And anecdotal evidence suggests so do most people.  So that is what we are going to talk about.

I said this is like any other cooking or baking.  So instead of a cocoa bean, let’s talk about roasting a hunk of meat.  Or loaf of bread.  Either works fine.  I’m picking those because they are usually 2-3 lbs, start at room temperature and come to some higher final temperature.

What is the classic way to roast these?  350 F oven for an hour is not uncommon for either one.

You put your loaf/roast into a 350 F oven.  Here is the first important thing.  The surface does not immediately become hot.  After 10 minutes, the surface is probably only 100 F and the interior is still room temperature.  And you are not surprised, right?  As time progresses, the heat sinks in.  Two inches in becomes 90 degrees, 1 inch in is 100 degrees and the surface is 110.

Notice the gradient?  That is how the whole roast is going to proceed.  At 30 minutes in the surface might finally be starting to get hot to the touch.  150-160 F.  But If you put in a thermometer to the center you will find the very center is still under 100 F.  Raw.

Not until nearly an hour later is the center getting to 150-160 F for a small roast and maybe 200 F for the bread. The meat has more water so it heats more slowly if you were wondering.

Roasting cocoa is the same.

But cocoa beans are not a loaf of bread I hear you saying.  Well, they kind of are.  They are a solid like mass in the pile they are in.  You can speed the roast along by stirring.  Distributing the heat.   This is exactly why I suggest stirring every 5 minutes.

And let’s look at a few other common things you bake.

Muffins or cup cakes.  350-375 F for 15-20 minutes.

Biscuits 400-425 for  12-15 minutes

What would have happened to either of those things if you had put them in at 250-300 F?  Totally under baked,  right?  Yep.

It’s all the same thing.  Cocoa behaves exactly the same.  Why wouldn’t it?  They are not magical.  It takes quite a bit of heat and time to heat them all the way to the center.

You are worried about burning them at 350-400 F I hear you say.  You notice that gradient I talked about?  That is why they don’t burn.  The oven can be 450 F even at the start.  The only way for the bean (or you bread) to burn is if the whole entire thing is that hot.  But it isn’t.  The heat is continuously sinking in, in effect keeping the surface from burning.

I know many of you are shaking your head in disbelief.  This isn’t just my theory.  I spend a few weeks recently testing just this.  Look a little of the data.

Temperature plot

Those are actual surface temperatures.  From everything we have seen the interior has to be cooler.  They don’t have a choice.  Absolutely none of those beans were even close to burned, let alone even over roasted.

What that means, even at 300 degrees for 30 minutes, your beans probably never made over 150 F on the surface.  Which means 100-115 F inside.  Raw by any definition for the majority of the bean.

That is why they were so sharp and astringent.  They were massively under roasted.  They were still raw.

It’s really that simple.  It takes a lot of heat to roast cocoa beans in any reasonable amount of time.  And to keep it to a reasonable time, you have to have a hot environment.  Heat flows and how fast it flows is proportional to how big the difference is between your beans and the oven.  At 300 F, although it seems hot, it  isn’t that different from your target of 250 F.  The consequence is it takes a long time to get there.

Just think about baking bread or a roast of beast and go from there.   Be fearless.

So get the beans in the hot oven.  Stir them often to help the heat distribute.  Take temperature readings (I use this IR thermometer) and stop worrying you are going to burn the beans.

Be fearless.  It’s only chocolate.