Double Roasting

Double Roasted Coffee

The Surplus Dilema

One of the happy problems I’ve run into with running my own business is an overabundance of coffee. Through Hoos Coffee Consulting, I often help clients dial in their roasts. And most of the time, they don't want to take back all the coffee they’ve shipped for test roasting in my training space. So I have a lot of leftover coffee of various roast styles and origins from all over the world. Additionally, with the Iteration Coffee program, where I create box sets for people to taste, I end up with a lot of coffee leftover from experiments that I make before releasing the boxed sets. Combine these two aspects of my business and I typically have a fair amount of leftover light-roasted coffee that I donate to local nonprofits, schools, teachers, and other organizations. 

An issue I’ve run into, though, is that my clientele are usually focused on roasting light, and my boxed sets tend to focus on roasting light as well. However, in my area, light roasts aren’t as highly regarded as dark roasts. So, even though I have a lot of coffee to give away, it doesn’t always match the preferences of the people I’m donating to. 

This led me to experiment with re-roasting light-roasted coffee to transform it into a more approachable dark roast for donating within my community. Along the way, I found that my previous ideas about re-roasting coffee and what makes a quality dark roast were challenged. I, and others in blind tastings, have found very enjoyable qualities coming from these double-roasted dark roasts. Sometimes, even preferring them to single roasted dark roasts in head-to-head blind tastings.

Paths for Dealing with Excess Roasted Coffee

My problem is similar to what other roasters face daily. Whether it is experimental roasts made dialing in a new coffee, roasted coffee that isn’t selling as fast as we would like that “ages out,” or something that falls outside of your product lineup, sometimes roasters end up with product they are not quite sure what to do with. Historically, there have been a few paths that people have taken to remedy this:

1. People don’t care and ship it anyway. While no one will likely fess up to this one, sometimes people decide to ship the coffee anyway. If you’re taking this action, it may be worth asking yourself what quality parameters you are looking at and whether you’re wasting your time over-measuring if those measurements don’t impact your decision.

2. People do a “blend back.” Sometimes, when a coffee is off base but perhaps still salvageable, a roaster will blend small percentages of it in with other versions of that roast to effectively hide any flavor/profile differences. This can be more common with coffees that are roasted with great frequency, but I’ve heard of it applied in various situations.

3. Sending it to a less stringent product stream. We used to have a saying: “f$&! It it’s frac,” or “frac it, it’s f$&!ed.” Frac was referring to fractional packed coffee (aka portion packed coffee), where the coffee is ground, left to off-gas, packaged, and then frequently warehoused until a customer is ready for it. Sometimes, this would be 60-90 days post-grinding. After being ground for such a period of time, the coffee was still good, but all the nuance was gone… so substituting roasts that missed metrics (but were still good) was deemed acceptable. 

4. Donations is another line that is utilized heavily. When a coffee doesn’t meet the standards, it is donated somewhere (501(c)(3) or some other organization). This can be a great way to help the community by providing above-average coffee that didn’t work out for your brand… that being said, the flavor profile may be a bit outside of the expectations of the consumers.

5. Finally, sometimes people just composted or threw coffee away. This I don’t understand. Unless the coffee is dangerous to drink (mold issues or something) it is best to donate it.

6. There are likely other ways I am missing…

Another suggestion could be to create a beautiful dark roast with your light roast coffees that didn’t pass the bar! A member of one of my mentorship groups (Jonathan Edelman) called this late-stage product differentiation. By doing this, you can find a home for otherwise great coffees that you can’t move in your normal product line, reducing waste, and making customers happy.

Caveat… Dark roasting well takes skill…

As I have spoken of at length through my work “Exploring the Dark Side,” dark-roasted coffee is not something that ought to be scoffed at or dismissed as low-quality coffee for the masses. If you’d like to read my thoughts on that, you can purchase a copy through my website [hoos.coffee/shop] and join the conversation. I make this mention now because, on first pass, it may seem like I am suggesting that we can just take unacceptable coffees and re-roast them, and dark roast people will be absolutely happy with the outcome. I am not suggesting that proper and good dark roasting is easy, an afterthought, etc. 

So, as we continue in this conversation, please keep that in mind.

What I’ve dabbled with so far…

So far, my experiments have been within a small range of coffees… but the results have been exceptionally promising. Because of the coffees that clients have been using and the coffees that I am roasting for the Iteration.Coffee boxed sets I have been working with, testing has only featured a small set of the global coffee range:

• Above baseline Specialty Grade (84+) Arabica

• High grown (majority > 1200 masl)

• Predominantly Washed (though I’ve done it with a wet-hulled Sumatra too)

• Roasted within the last four months (roughly)

• Coffee that was initially light to medium in roast degree

It is important to note the limited range that I’ve experimented with here because I don’t want anyone to think that they can do this with any coffee and come up with positive results (though I suspect it could work with Robusta, too). If you are using coffees that fall outside of these specifications, I cannot speak with any real practical experience as to what your results may be. That being said, I have some theories (which will need testing, of course).

Why I think it works

Here may be why this works out:

1. People who appreciate dark roasted coffees tend to like lower acid coffees with dark chocolate, nutty, caramel, and smokey notes to them. I suspect that re-roasting coffee does a lot to squash the fruitiness and acidity of a coffee, as these more ephemeral characteristics tend to be muted with longer roasting and development times (so you could imagine that roasting them for a second time mimics this). Is it baked? Is it muted? Maybe, but it fits the bill for the flavor profile many are expecting. 

2. Because these coffees haven’t entered into some of the pyrolytic chemical reactions yet, the reagents are still present and able to react in similar ways to those we experience when roasting a coffee only once. This is why I feel unsure about this tactic working well when re-roasting a dark or light roast light to the same general roast level it was before. The roasting process needs to have novel chemical and physical reactions for it to be a useful “double roast.” 

3. Because life is one surprising wild ride.

How I approach double roasting:

My approach for double roasting a coffee starts with the following assumptions:

• The coffee is already low moisture content (1.5-3% would be my guess) and therefore does not have as significant of resistance to absorbing head as a green coffee would. 

• Because of the coffee’s low moisture content and more fragile structure, it will be prone to roasting defects like tipping, scorching, and facing. Even when re-roasting coffees, there are good (flavor-driven) reasons for avoiding physical roasting defects. For more info on these, check out my blog post on roasting defects: hoos.coffee/blog/putting-names-to-things 

• Based on the above notes, I don’t need to charge the roaster very hot.

• Based on the above notes, I will not use the higher register of the burner capacity of the roaster.

• I’m in no hurry to roast this coffee and will still aim for ~ 4:00 development time (read: Exploring the Dark Side) after hitting the first crack at the 9-10 minute mark.

• Because I don’t want to overload the machine, I need to bring weight loss calculations into the mix to make sure that I am adding the appropriate amount of coffee to the drum.

Essentially, the way I conceptualized it is that I want to charge low and run my burner only as high as I would be willing to run it post-first crack if I were making one pass at roasting this coffee. On my drum roaster, I am also choosing to run the airflow at 64% because it helps me pass heat energy along to the coffee without getting the drum too hot and causing facing/scorching. This is something that may or may not translate over to your coffee roaster. 

Examples of me doing this:

Here is an example of me running a traditional drum roaster:

Please forgive the random thermocouple noise I experienced around 4:30 to 5:30. 

Here is an example of me roasting on my Loring s7:

Generally speaking, the weight loss of the coffee before hand was probably in the 11-13% range. My weightloss % going from roasted to dark roasted tends to be ~ 6%. I’ve bounced around mostly between 5.5% and 6% weight loss, which is more variability than I would like… but it is incumbent on the amount of initial moisture in the green as well as the degree of roast of the light roast before it.

For further study

I don’t lay any claim to this being a done concept. I am not the first person to ever re-roast coffee either… We’ve all likely run into someone who is doing it already. I want to find a way to systematize double roasting a coffee so that it produces consistent, good results. I also want to de-stigmatize it to a certain degree and offer people the chance to experiment with it themselves. Here are things that need further study:

• How old is too old for double roasting a coffee? Ex. Once coffee is > 6 months past its first roast date, the age will show up in the double-roasted product. I’ve used some pretty old coffee and still had it taste nice as a dark roast… but I haven’t intentionally experimented with this.

• Will this work for other processing methods? I’ve primarily worked with washed processed coffees. How will this work for a natural, honey, or anerobic coffee?

• Will this work for all growing altitudes? I’ve mostly experimented with higher altitude lots, so it’s possible this won’t hold up across various elevations.

• Will this work with old green? Can double roasting help reduce aged flavors from past-crop coffees, or will they taste past-crop regardless of how many times you’ve roasted them?

There is doubtlessly more to add to this, but for now, what I really want to encourage you all to do is to try this. 

Ready to Try Double Roasting Yourself?

If you have some light-roast coffee that didn’t quite hit the mark, try transforming it into a dark roast using the methods I’ve outlined here. Experiment and share your results with me—I’d love to hear about your experience or answer any questions! Feel free to drop a comment below.