There are few things as humbling as trying to learn how to roast coffee. It might seem simple enough, but it’s a complex skill that very few people have mastered. Thankfully, coffee legend Scott Rao has finally published his magnum opus, The Coffee Roaster’s Companion. The book is the culmination of over 20 years of coffee roasting experience. Don’t be misled by the slim profile, the content is dense enough to engage a seasoned professional while the style is approachable enough for hobbyists. Over the last 9 months, I’ve read and re-read this book. Sometimes with eager curiosity, other times with frustrated desperation. The book is nicely balanced between technical theory and practical advice. Years ago, Rao’s The Professional Barista’s Handbook was formative for my barista career. The Coffee Roaster’s Companion has already proved to be as influential.
Unequivocally, if you have any interest in roasting your own coffee, you should buy this book. You may not agree with everything Rao has to say, but you will find your own opinions sharpened and informed by Rao’s careful thinking. Here are the top five things I learned from Scott Rao about coffee roasting.
1. Watch Your Rate of Rise
If you don’t like math, coffee roasting may not be the best hobby or profession for you. One of the most important metrics for mapping and evaluating a roast is the rate of rise (RoR), which Rao defines as “the progression of bean temperature per unit time during a roast.” Essentially, a good roast has a steadily decreasing RoR. Roasts that stall or digress develop unpleasant “baked” flavors. Conversely, roasts where the RoR increases, especially after first crack, tend to lack any sweetness.
2. It’s all about development
Rao hates the phrase “development stage”, which traditionally is used for the amount the coffee is roasted after first crack. According to Rao, development, i.e. the breaking down of the coffee bean’s cellulose structure, occurs during the entire roast. In fact, the early stage of roasting is crucial for proper inner bean development. “Low and slow” might be the secret to good barbecue, but coffee needs a large amount of energy upfront.
3. Minimize use of the trowel!
There’s nothing like taking out the trowel and inhaling all of those amazing aromas that occur during roasting. But according to Rao, it’s the last thing you should do. Using the trowel decreases temperature stability in the roaster, and ensures the coffee in the trier is not going to follow your desired profile.
Editor’s note: The Coffee Roaster’s Companion does not contain the above information, but was inspired by talks that Scott Rao has done. We regret the error.
4. Increase the airflow as the roast progresses
The higher the airflow, the higher the convective heat transfer (as compared to conductive heat transfer.) As such, airflow should be gradually and incrementally increased as the roast goes on. This dispenses of the smoke and chaff that are produced late in the roast. According to Rao, smoky flavors in the cup are a sure-fire sign airflow was set too low.
5. Cupping is King
The best way to evaluate your roasts is cupping. Developing a palate that can identify roast defects is one of the most important skills a coffee roaster can possess. This only comes from extensive, thoughtful tasting. Worth the price of the book is the chart on page 65, which maps unpleasant flavors with certain roasting errors and how to fix them.
If you’re fortunate enough to have access to a refractometer, Rao recommends cupping at the same extraction percentage as your ideal brew. If you’re not able to get the extraction percentage you wanted, this is an indicator your coffee wasn’t sufficiently developed.
For more information on cupping, check out the Specialty Coffee Association of America’s cupping manual.