Most cocoa beans that you will encounter for chocolate making are fermented, but are not roasted yet. The fermentation process does darken them up considerably and you may think they are already roasted, but the lack of an evenness in color and texture is the key to telling when they are unroasted. Roasting accomplishing a number of things.
It helps separate the outer husk from the inner bean and makes cracking and winnowing much easier.
It also virtually sterilizes the cocoa bean. This is rather important as the conditions in which cocoa beans are fermented are naturally full of bacteria, fungi and molds. There is a "quantifiable" risk of infection from unroasted cocoa beans. Roasting reduces this risk.
Various chemical reactions occur when cocoa beans are roasted and proper roasting is integral to good flavored chocolate. The vinegar smell from fermenting is driven off. Raw beans don't taste like chocolate. Roasted beans do.
Finally, for those of you who have read about the nutritional value of chocolate and cocoa beans, and worry that roasting destroys these nutrients, please remember that all of the research (to the best of my knowledge) has been done on fully roasted, fermented cocoa beans and chocolate. Sure, if you over roast or over process it, you may well loose some nutrients, but I personally take the nutritional benefits of chocolate as a benefit, not a goal. The flavor is my goal at Chocolate Alchemy.
Options for Home Roasting Cocoa Beans
There is a ton of information out there on the web about roasting coffee at home. If you can roast coffee at home (I do), you can roast cocoa beans at home. Sweet Maria's is a great source for coffee roasting information and some supplies.
Unlike coffee, which roasts anywhere from 400-460F, cocoa beans need more gentle treatment. In that there are no hard or fast coffee roasting rules, the same holds true for cocoa. In general though, they can be roasted from 5-35 minutes anywhere from about 250-325 F. To do this, there are basically five options:
Drum roasting with a gas grill
Coffee roaster (the Behmor is our pick)
Hot air gun, believe it or not.
With all of the methods, the basic technique is the same. Subject the cocoa beans to a high temperature initially, slowly reduce the temperature and stop the roast when the beans are "cracking", but well before they start to burn.
The initial high heat lets the beans gain some thermal momentum and allows for a good separation of the husk and nibs as the beans expand. You lower the ambient temperature so as not to burn the outside of the bean, but let the interior continue to roast. Finally, the cocoa beans will start to pop and crack as water vapor is explosively released. This happens when the cocoa bean temperature is around 250 F. This is your sign you are just about done roasting. Experience and smell (you don't want any burned smell) are the key indicators when the beans are roasted. Once the cocoa beans are roasted and cooled, try separating the husk from one. If it comes off easily, you did well and the beans are fully roasted. Likewise, taste some. They should have a nice cocoa flavor, with no raw or burned flavors.
Generally I like to have a roast take 15-20 minutes, regardless of method. Under that amount of time and the beans seem to retain a raw unfinished flavor. Over that and they start to taste baked and sort of flat.
Criollo (because they are light in chocolate and fruit) tends to benefit from a more gentle and end with a lower temperature, where as Forastero MAY need more aggressive roasts with a higher end temperature when they are big on chocolate and fruit. So far I have had a reasonable degree of success at keeping the roasting under 270 F and stopping the roast before the "baking chocolate smell" goes away. Overall, don't take them too hot, but experiment and roast a lot by smell. If it smells like chocolate, you are on the right track.
That I am aware of, virtually everyone has an oven in their kitchen, and you can roast cocoa in it.
Here is an excerpt from one of my (ancient) logs. You can see how I have slowly dialed in what temperatures to set the oven at and how to adjust it.
Alchemist John's Oven Cocoa Roasting Log
In general, if you try oven roasting, you will start hot (350-400 F) for a short amount of time and slowly lower it to your target temperature (275-300 F). This is for about 2 lb/1 kg of beans. The more you are roasting, the higher your initial temperature can and has to be and the time will probably be a little longer.
Remember, you want to roast the cocoa beans, not bake them. This is how that looks:
Whole cocoa beans
375-400 F 5 minutes
350 F 5 minutes
325 F 5 minutes
300 F for 10-15 minutes or until done*. Look for the aroma of baking brownies and/or pops. Both are good indicators you are there.
*For an even better indicator of a complete roast, use an infrared thermometer and roast until the beans show 250-260 F. Make sure you stir the beans before taking your reading so you don't have a high bias.
If you have nibs, you both can and need to take them a little more gentle.
350 F 10 minutes
325 F 5 minutes
300 F 5 minutes
275 F for 5-10 minutes or until done (again 250-260 F IR thermometer reading)
That is really it. Of course, there are LOTS of other ways you can do this. I know some people roast at 250 F (or even 220 F) for 45 minutes to an hour or even two. I am personally not a fan of this style, but you may be. And hey, nearly everyone has an oven.
If you are going to be serious about roasting cocoa beans at home, and/or making chocolate, this is the method I recommend. It has the most flexibility, consistency and gives the best overall product for the least amount of work.
You can either make your own if you are inclined or obtain one from RK Drums. These are both high quality stainless steel, sell for around $200, and will last a lifetime.
With any of the drums, you will roast on a gas grill, with a thermometer inserted just below the drum and rotate the drum with a generally available motor or rotisserie that rotates anywhere from 6 to 60 rpm.
I pre-heat mine to between 350 - 400 F, and load anywhere from one to four pounds into my drum. Once the grill is up to temperature, I place the drum into the grill and start it rotating. You will see the temperature drop of 50-100 F depending how much you loaded. Resist the urge to turn the temperature up. Just let it come back up over time. After about 10 minutes, you should start to notice a nice brownie smell and the ambient temperature should be back in the 300-350 F range. Don't let it get over 400-425 F as it can start to get out of control as the beans dry out.
In another 5 minutes the cocoa beans should start to crack. Give them about couple of minutes, smelling, judging and guessing when they are done.
Get your fire proof gloves on (did I forget to mention these?), remove the drum, dump the beans in a waiting bowl, and stir until just warm to the touch.
This is what a previous non-too-glamorous setup looked like. The drum very comfortably roasts 3 lbs and could probably do as much as 4 lb or as little as one.
Drum roaster on the grill all loaded with 3 lb of Ocumare
Dumping the beans after a 13 minutes roast
All cool and waiting for the next batch
These are a little dark on the outside (see below why), but really fine inside
This was my third batch and actually, this roast got a little out of control. The collar holding the drum closed slipped (now it has a new collar) and some beans dropped in causing a very smoky fire, hence the sooty appearance on the beans. Since I consider this just about the worst I could do, I figured I would go ahead and process these into chocolate and see just how it comes out. It is often said that cocoa beans have a narrow window of good roasting, but these tasted pretty good. Mostly, they are not pleasing to the eye. By the time everything had rested, mellowed and melded, the chocolate was just fine with no hints of smoke or off flavors.
There are only two off the shelf coffee drum roasters that I know of that can do a reasonable amount of cocoa beans on a small scale. The Behmor 1600 and the Hot Top. Between the two, there is just really isn't any contest. The Hottop will do 6-8 oz of cocoa, maybe 12 oz if you push it. The Behmor 1600 plus can do 2-2.5 lbs.
With both of them you will need to judge when the beans are finished and stop the roast manually as they are programmed for coffee. I have not had the opportunity to experiment with the Hot top in a number of years, so I can't really speak about it's current level of programming. The Behmor on the other hand, I have worked with a lot. It has 5 roast profiles, that are all suitable for cocoa roasting.
Now, in the same way you can use a Behmor 1600 Plus, you can use pretty much any commercial drum coffee roaster if you have the use of one. There is no cross contamination of taste either. I roast coffee and cocoa in the same roaster and both taste as they should. I personally use an old Royal #5 which runs off propane and can handle 15 lbs of coffee. But because cocoa roasts so much cooler than coffee, I routinely roast 30-35 lbs of cocoa.
As a rough temperature profile, I pre-heat to 350-400 F, and drop in my cocoa. With a thermometer in the bean mass, the temperature usually drops to the low 100's. I then roast, adjusting my heat, to reach 250-260 F over about 13-18 minutes. Yours of course may vary, but as a bench mark, for me, the beans just start to crack in this temperature window. So if yours shows 300 F or 240 F, fine, that is roughly your 'new' target temperature in 13-18 minutes. And those time and temperatures are not set in stone - they are to give you a guideline to work with, and then adjust off of after you have made it into chocolate. Too sour? Try a little longer and/or hotter. A little acrid? Try dropping your final temperature a bit. To acidic and acrid? Roast it a bit longer (to reduce acidity) but do it more gently (to reduce the acridness). Get the idea? Hopefully so.
Profile Drum Roasting
I have developed a method of Profile roasting cocoa that is remarkable similar to the profiles used by coffee roasters. You have a drying, flavor development and finishing phase.
In lieu of repeating (for now) what I have written in great detail, I recommend you go read Ask the Alchemist 200 through 206. I go into each phase in great detail and how you can adjust each one to reliably alter the flavor profile of your chocolate to suit your tastes.
I want to make it VERY CLEAR this is about DRUM roasting and can NOT be applied to oven (even convection) roasting.
This is only kind of an option for roasting cocoa beans. I mention it only because I use a modified West bend popcorn popper to roast my coffee in at home, and for a couple of ounces of cocoa beans, it works well enough.
It is not really a practical way to roast a large (or even a moderate) amount of cocoa beans and nibs tend to fly out.
Regardless, what I do is toss in a couple of ounces, turn on the heat, and watch the beans swirl around. In 3-5 minutes, they are usually cracking very loudly and I turn it off and cool them down. Good enough for token evaluation purposes but it is a little to fast and hot for a proper roasting.
Hot Air gun
This again is from the realm of coffee roasting. It is not high tech, but it gets the job done. Basically, place 1-2 lbs of cocoa into a shallow bowl (the coffee roasters use a dog bowl, really), use the heat gun to heat the beans, while you manually stir them. In the same vein as before, add a lot of heat initially, back off as the roast progresses, and stop when cracks are happening and it still smells like baking brownies.
I will be updating this particular method as I get more experience.