roast profile graph - temperature over time

Roast Profile – Managing Heat and Time for Better Coffee

Better Coffee

A roast profile that’s stock will lead to stock coffee. You can buy stock coffee pretty cheap these days. Cruise over to your local grocery store and grab you a can. In it, you’ll probably find pre-ground coffee that was roasted some time last year. They used a one-roast-fits-all profile for their low quality beans. The result? Bitter, flavorless, stale, flat, gross coffee.

We can do better.

To start with, we source our beans with integrity and care. We only serve specialty coffee of very high quality. We also deliver it to you fresh, with published roast dates on the bag. The step in between is the most difficult of all: roasting it well.

Managing the Roast Profile

“Geology is the study of pressure and time. That’s all it takes really…pressure…and time. That…and a big [%$#@%] poster.” -Red, The Shawshank Redemption

This doesn’t have much to do with coffee, but thinking about profiling my roasts reminds me of this quote from one of my favorite movies.

Roast profiling is a management of heat and time. A coffee roast typically lasts from 8 to 12 minutes long. Mine usually run about 9-10 minutes. During that time, the coffee beans go through quite a lot of change. I observe these changes in 4 very different stages: Drying, browning, first crack, and development. Some roasters have a 5th stage: the dreaded second crack. For me though, the second crack is like a warning light in the car. If I see it (hear it), something’s wrong, and I’ve burned an entire batch of coffee.

The stages of the coffee roast are incredibly important because the temperature should rise at different rates during each stage. For example, the drying stage experiences the most intense heat with an average rate of about 30-35°F per minute. On the other hand, the development stage will see a much more subtle increase in heat with an average rate of about 5-10°F per minute.

What’s at Stake Here?

What is a good coffee roaster trying to avoid?

  • If heat doesn’t rise rapidly enough during the first stage, the bean will turn out under-developed. This happens when the interior of the bean isn’t roasted to the same level as the exterior. Think of a rare steak. The result is a very sour, grassy, and unpalatable coffee.
  • Some roasters will avoid an under-developed roast by simply roasting it longer. They take their coffee into, and even deep into, the second crack to make sure they sufficiently roast the interior of the bean. The result here is coffee that tastes very burnt and smokey, like charred BBQ and second-hand cigarette smoke. You might actually be into those kinds of things…
  • If too much heat is applied throughout any part of the roast, the coffee will be burned, and fire might break out! We must avoid this, obviously.
  • If too little heat is applied throughout any part of the roast, you got it, the coffee will be under-developed.
  • There is something called developed but baked. This is when the bean roasts all the way through, but at some point the heat increase has stalled or the development stage went on for too long. The result is that the coffee has very little flavor, a weak aroma, and maybe even a paper-y taste.

The Aim

On the other hand, there are wonderful aspects that coffee can have when the roaster is on his or her game. To begin with, the aroma and fragrance smell incredible with craft coffee. The aroma will easily fill the room. Next, and probably most obviously, craft coffee offers some truly remarkable flavors. A coffee’s flavors are supposed to be there without soaking the beans in flavor oils such as pumpkin spice or hazelnut. Coffee beans should have inherent flavors, given to them by nature, not by man. These flavors include very positive tones like nutty, chocolate, brown sugar, fruit, vanilla, cinnamon, honey, etc. Craft roasted coffee can give lots of good feels too, such as bright, smooth, creamy, or light. The roaster can preserve or annihilate all of this pleasantness with the roast profile. Carefully manage the profile, and expect incredible results in the entire experience!

The Learning Process

Mastering the roast profile isn’t a one-time thing. Everything changes, from ambient temperature to atmospheric pressure and beyond even to the bean itself. Different coffees will change in flavor, density, and even quality from crop to crop. I’ve made a promise to my company and customers that I will keep learning and growing, and that I won’t stop criticizing myself to make my product better. It’s a constant process that I’m thrilled to be a part of. Send me any questions you have, especially if you notice something you would like me to improve with my coffee.

  1. Don Bellenger says:

    Is the graph at the top supposed to indicate temperature during the roast? Temperature delta? Either way, it seems at odds with what you’re laying out when you describe the first stage. Also, wouldn’t a higher temp result in a more uneven roast?

  2. The graph is actually just a drawing, a depiction of how the temperature of the beans increase at different rates throughout the roast, that’s all. The delta temp graph actually shows this, starting off very high for a minute or two after turnaround and gradually decreasing as the roast progresses.

    It’s said that the higher the delta temp during the drying phase, the better developed the coffee will be. But you’re right, if you have too high of a delta temp at first, you risk scorching the beans, so there definitely is a balance.

    An uneven roast could also be caused by poor quality beans, too high of a charge for the size roaster you have, improper drum speed, or poor airflow (mostly with air roasters).

    Thanks so much for your comment!!

  3. Roaster says:

    Really enjoyed your article! I have a small “sample” roaster [ Kaldi Wide ] that uses a perforated drum . There is little thermal mass to the roaster itself and is made from stainless steel. Airflow is controlled by what naturally occurs throughout the roast which exits through the hopper on top and also vents on side. I use a portable 12000 BTU butane stove for my heat source. The roaster has a max load of 300g. The manual said to charge drum at 400f . My typical roast is 150-200g . With that being said, my question for you is: if I am charging with 150g, should my charge temp go down? Any recommendations ? Thanks so much!

  4. First, I’m not familiar with the Kaldi Wide, so take my recommendation with a grain a salt.

    The charge temp (as well as the residual thermal capacity stored in the roaster) is the starting energy you’re using to pull the beans up to an optimal roast level, and the relationship between the thermal energy of the roaster and the bean temperature is elastic. So if you use a 400* charge temp for a 300g batch and you’re getting excellent coffee, then yes, you’ll use a lower charge temp for a smaller batch. If you can control drum speed, I would lower that as well. You need to track your rate of rise throughout so that you can make sure it’s not too high with the smaller batch size. If it is, try a combination of lowering the charge temp and letting the batch “soak” a little, 30 to 45 seconds, to reduce the energy in the drum.

    This is pure speculation though, I don’t mess with batch size at all. When I did, I would get a very uneven roast and it would have ash and char notes in the cup. I would stick with the batch size that was recommended to you by the manufacturer and try to perfect your profile with that.

    Thanks so much for your comment!!

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