Roasting Decaf Coffee – Some Key Things to Know

Even for an experienced coffee roaster, decaf coffee can prove challenging. Here’s why …

Decaffeinated coffee has been steadily improving in quality, and we think the time has come to let go of the “death before decaf” mentality. Almost all of the decafs we sell at Sweet Maria’s are decaffeinated using the Swiss Water Process (“SWP”) – this chemical-free method is gentler on the coffee’s organic structure and leaves much of the volatile compounds that affect aroma and flavor intact. For more info on the Swiss Water Process, check out our Swiss Water Process FAQ

Does the decaffeination process affect flavor? Of course – it would be dishonest to suggest otherwise. Even with improved processing, there will be a difference between the regular and decaf version of a coffee; we recently had the chance to compare the same coffee with regular and decaf side by side.

Comparing green coffees side by side; non-decaf top, Swiss Water Process decaf middle, and CO2 decaf at bottom.
Comparing green coffees side by side; non-decaf top, Swiss Water Process decaf middle, and CO2 decaf at bottom.

For this reason, roasters will rarely choose their best coffees to be decaffeinated – doing so would be like burning money! Luckily for Sweet Maria’s, we don’t face the same challenge and, as a result, all of our single origin decafs have a cupping score of 86 or higher even after decaffeination. For us, decaf is not a second-class citizen in our coffee line-up.

Given our high quality decaf, home roasters who drink decaf might experience an even larger jump in quality from store bought alternatives compared to those home roasters that stick to regular. 

Have we convinced you to try your hand at roasting decaf coffee?

Here are a few basic things to keep in mind as you get started: 

Why does my decaf coffee look darker while roasting?

Don’t trust color change as an indicator of roast level. Decaf coffee can get very dark, very quickly, but that does not reflect the actual roast level. In fact, decaf is already a darker shade than non-decaf coffee before roasting. While the Swiss Water Process does a great job of leaving the volatile compounds in the coffee intact, decaffeination weakens the internal structure of the coffee. Due to these changes, you’ll notice a different color progression – the beans will shift color from “green” (unroasted), to brown to dark brown very quickly, well before the coffee approaches first crack. Similarly, the surface texture of the bean will stay somewhat wrinkled, rather than smoothing out as you roast darker. 

What’s a good comparison when roasting decaf coffee?

Roast a similar, regular (caffeinated) coffee. Since judging the roast level of decaf can be difficult, we highly recommend roasting a regular, caffeinated coffee from a similar region and of the same varietal. Decafs tend to roast similarly to regular counterparts, despite differences in roast level indicators (color change, etc), so having a go-to profile for a regular coffee provides a helpful baseline for your reference. The decaf might turn out a tad lighter or darker than the “regular” coffee, but you will be in the ballpark.

Tracking the roast color changes of non-decaf, and Swiss Water Process decaf coffees.
Tracking the roast color changes of non-decaf, and Swiss Water Process decaf coffees. 1: Wet Process Ethiopia 2: Swiss Water Process decaf Ethiopia 3: Swiss Water Process decaf Brazil

Do decaf coffees have the same audible snaps as regular, non-decafs?

The snaps of first crack tend to be slightly softer in decafs, so you can miss them if you aren’t paying attention. Do your best to note the start of first crack, since timing your roast after this benchmark is one of the easiest ways to determine when the coffee has reached your desired roast level. 

I only roasted to City+, so why is my roast so oily?

It’s normal to see oil on the surface of your roasted decaf coffee. Like we mentioned a little earlier, decaffeination breaks down the organic material in coffee, which makes for a more porous cell wall. Because of the this, moisture escapes more easily during the roasting process, and oil will rise to the surface post roast, even when the coffee is roasted light.

What other ways can you monitor roast development?

Pay attention to smell. Once you’ve entered first crack, you’ll notice a sweet, almost vinegar-like aroma. This is a sign that your coffee is sufficiently developed – of course, you can roast darker if you’d like, depending on preference. Be sure to move past the yeasty, bready aromas noticeable in the drying stage or you might under-roast – this is particularly important if you’re aiming for a lighter, City/City+ roast with a decaf coffee. 

A pallet of Costa Rica coffee in GrainPro-lined jute bags that was decaffeinated by Swiss Water.
A pallet of Costa Rica coffee in GrainPro-lined jute bags that was decaffeinated by Swiss Water

Do decaf coffees benefit from a particular roast profile?

This concept is slightly more advanced, but helpful to keep in mind. If you have manual heat control, be careful with energy input during the drying stage and again at first Crack. Decaffeination weakens the internal structure of coffee and makes it less dense. Decaf coffee can take on heat more quickly as a result and, if you aren’t careful, first crack can take off, and quickly get away from you. A good rule of thumb is to pull back energy input (using heat or fan settings, depending on your roaster) just before hitting first crack. 

Can I expect similar weight loss from roasting as a non-decaf coffee?

The short answer is, no. The decaffeination process removes some of the coffee’s mass, and so the coffee stands to lose less weight during roasting than a non-decaf. Seeing even a couple % difference is totally normal. I’ve had decaf City roasts measure at 9-10% loss, whereas that would be 12% loss in a non-decaf. All coffees are different, and expect some variance in numbers.

What else can I do to improve on roasting decafs?

Take notes and learn by trial and error. Roasting theory is always helpful, but the best way to improve is through repetition. This goes for all roasting, but is especially important when roasting decaf. Time your roast and take careful notes of changes in color, aroma, and temperature (depending on your roaster). What changes to your heat, airflow, etc did you make throughout the roast? Always note when first crack starts and ends. Once you’ve had a chance to brew the coffee, write down your impressions – was this a successful roast? Does it taste underdeveloped, or overdeveloped? The more data you collect, the easier it will be to improve future roasts. 

14 Responses

  1. Just wondering. I have a two pound roaster. Can I roast half regular and half decaf together. Or will it change the flavor.

    1. Yes – you can definitely roast the coffee together. Decafs do color a little differently as they roast, but your non-decaf coffee can guide you to the roast level you want…

  2. Great question that introduces using the non-decaf beans as a guide. I can use that.
    It also produces and answer for me with some friends who like half/half coffee these days. I can roast it half/half. Just have to come up with a name for it. Ideas?
    “Low Dose Coffee” / “Half Caf” / “… ?

    1. There is not one answer, but it can be slightly less than non-decaf in drum roasters. The trick is in estimating the degree of roast … hence the article.

  3. When make a coffee blend, always roast the beans seperately then combine them. Since different beans will roast differently (especially decaffeinated beans, which roast quicker) you would get some over roasted and some under roasted if you roasted them together. If you’ve tried it and you like it, however, you can roast any way you like,

  4. I just roasted 2 small {4 oz) batches of Ethiopian decaf in my air roaster. I play a guessing game using visuals and smell ( since my hearing is diminished, the “crack” is not workable). I wasn’t aware that the roast color would be so different with decaf beans. Now I need to do a roast of similar “caf” beans and see what I notice. Thanks for the tips.

  5. I have watched several tutorials and went with one from Sweet Marie using an Air Roaster when I did my first roast and have been using the same instructions thus far. In the tutorial he roasted past 2nd crack, so now I am confused because the more videos I watch and the more I read I only see referrals to 1st crack. Should I roast to 2nd crack and do I wait until 2nd crack is finished before I stop? My times for roasting vary greatly from 8 minutes to 20 minutes (if going by crack). I roast both regular and decaf. Is there one basic rule of thumb to go by while I am figuring out how to do this?

    1. Hi Kathy,

      Thank you for your comment! First off, here is a helpful primer on the differences between 1st crack and 2nd crack, how to identify, and impact they have on flavor.

      The short answer to your question of whether or not you should roast to 2nd crack all depends on flavor preference. At 1st crack, roast flavors will be less pronounced, and flavor nuance comes through a little more clearly. Once you reach 2nd crack, roast flavors dominate the brew, and you have a more typical dark roasted coffee. One is not better than the other. It just depends on what you like!

      I hope this is helpful. Please feel free to chime in with any other questions you may have.

      Cheers,
      Dan

  6. I am new to roasting, and I’m using a popcorn popper. I have been weighing my beans before and after to get an idea of water loss. My scale only rounds to the nearest gram, and since I’m doing 100g per batch, this isn’t really accurate enough to differentiate between, say, full city and full city +, but I do it anyway. Generally 100g of green coffee produces 85-86g roasted coffee. I recently did a batch of decaf, using my normal method and normal time (7:30). 100g of green decaf produced 90g of roasted coffee. Additionally the roasted decaf beans looked very similar to my roasted regular beans, rather than looking darker as you indicate in the article. Confused, I threw the beans back in the popper for an additional 2 minutes, which produced very little change in color and no measurable loss in mass. (Maybe the popper never really got through the warm up period in that 2min). Is there any reason decaf beans would actually take longer to roast in a popcorn popper? And/or that they would lose significantly less mass at a given roast level than a regular bean? Should I conclude that my beans are less roasted than my regular beans? I have not yet ground them to see a grind color. Maybe that would answer the question..

    1. Hi Nancy,

      Thanks for chiming in on the post with your question. It’s a really good one, and something that should be clarified in the article. Decaffeinated coffee has already had some of the mass removed during processing, so there is a lower yield loss post-roast. Every decaf is different, but I would generally expect a higher return than non-decaf. (That’s a point often drive home to production roasters in a way to help justify the higher cost of decaffeinated coffee). Decafs are tough at first, and I think it just takes a few trial runs for anyone new to roasting them in order to find your footing.

      As for throwing the batch back in the Popper, while the roaster heats quickly, it will take the cooled beans a lot longer to come up to temp. It’s never ideal to put coffee back in the roaster, but doing it quickly – before the coffee has cooled – gives you the best chances of success.

      Hope this is helpful. Please don’t hesitate to reach out with any other questions!

      -Dan

  7. Dear Sweet Maria’s,
    As always, Thank you for your instruction. It helps going forward. I made a trip to your retail shop in Oakland in 2017 before my wife passed away and picked up a Hario hand grinder, but I had been roasting your coffees for three years prior. I now roast professionally and brew all my coffees using an Aeropress. The Decaf instructions really help. Thank you.

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