Home Roasting – Part 4

2010 July 21

I always enjoy spending time in the company of fellow coffee enthusiasts. They are a committed and intense bunch, fueled into levity by consuming top quality caffeinated beverages. The discussion is unfailingly lively, centered around making the very best coffee. As a part of my home roasting experience, I decided to invite over my friend and earnest coffee disciple, Luis Till. The plan was to roast coffee a few different ways and evaluate the outcome. We were accompanied by our project photojournalist, Chanelle Richardson.

Luis is of Peruvian heritage and has a natural love for coffee. His brand is Amauta Coffee for which he has future plans. He is the ideal coffee man. For one thing, he is a continual learner, always trying learn from anyone who is willing to talk coffee. He also is open minded and not yet hardened into a dogmatic adherent to one coffee sect. Luis loves to roast and he has a very good cupping palate. We decided to meet up and roast one coffee (the Guatemalan Finca San Diego Buena Vista) on three different roasters to approximately the same degree of roast. The evening we met was probably one of the hottest in the Arizona summer: 106 °F and humid!

We started by roasting in the HotTop. Luis had never seen one in person, so before we started I gave him a tour of the features of the machine. He was impressed with the quality of the construction and the control system.

Since I wanted to be able to use the coffee in both an espresso machine and brewed, combined with the hard density of the bean, I decided to roast to a Viennese Roast. I used the normal roasting profile preset at the factory, but increased the final temperature (when the roasted coffee is ejected) to 424 °F up from the standard setting of 420°F. This results in the stopping the roast a few seconds into second crack. By the way, the indicated temperature on the HotTop is not the same as a true bean temperature. For more information on the correlation between indicated temperature and bean temperature, HotTop has a very useful graph. I was very pleased with the roast, as it spilled out into the cooling tray. The roasting time was about 17:00.

We then roasted with the hot air popcorn popper, which was the subject of “Home Roasting – Part 3”. Looking down the barrel we did our very best to try to match the roast color of the HotTop batch, which is very hard to do. It is a very fast roast, particularly with the starting air temperature of 106°F! The roasting time was 6:30 and the degree of roast was approximately the same.

It was Luis’ turn to roast. He brought his “old school” manual popcorn popper. Using the gas burner at our barbeque island, Luis preheated his popper. He has done many roasts using this popper and has developed an elaborate set of “rules of thumb” to ensure a quality roast. At just the right time, he added the green coffee and began vigorously shaking the popper back and forth. Watching the thermometer like a hawk, he would lift the pot on and off the heat as necessary to ramp the temperature.

Towards the end, Luis began cranking feverishly to keep the beans agitated and heated uniformly. It was harder to hear second crack, but we kept listening and watching the thermometer. At our best guess for similar degree of roast, Luis dumped the batch. The roast time was bout 14:00.

Luis uses “old school” cooling , as well. He deftly stirs the crackling hot beans in a colander with a wooden spoon. This helps separate chaff and fragments while cooling the beans.

Examining our work, we were rather pleased. We broke open a few beans to look at the cross section  and check the roast gradient.

In order (from left to right) are the HotTop roast, hot air popcorn popper, and manual popcorn popper. As can be seen from the photo, the HotTop and the manual popper had the best external uniformity. Also, both of the poppers were stopped a bit sooner and therefore are at a somewhat lower degree of roast. A reddish cast is evident in the manually popped beans, which would indicate the lightest roast of the three.

Cupping Notes

It is interesting to discern the differences created by both variation in degree of roast and  method of roasting. Since we used exactly the same coffee for each roast, that variable is constant. Luis and I each did cuppings at 24 and 48 hours for degassing. Luis used conventional cupping and v60. I used conventional cupping, Melitta pour over, black and with standardized amounts of half & half.


Joe – Clearly the darkest of the roasts, bittersweet chocolate and dark cherry notes. Heaviest body, nice and syrupy. Through the E-61 Faema after 5 days made into espresso and cappuccino: chocolate covered cherry flavor and syrupy; muted by milk, but still pleasantly  evident.

Luis – Well developed beans with cocoa notes. Caramelization notes evident. Chocolate porter-like flavor and mouthfeel. Legs like fine wine indicate heavy body and held up well in milk.

Hot Air Popcorn Popper

Joe – Relatively bright, fresh berry note. Medium/light body, did not have nearly the soluable solids and did not stand up well to milk. Lacking complexity, seemed underdeveloped, which may be a result of fast roast times.

Luis – Some cocoa notes and possible smokiness. Light body and lacking in complexity. Noted that some of this may be due to inability to control the roast and hit exact degree of roast.

Manual Popcorn Popper

Joe – Chocolate and dark cherry notes with more forward fruit than the HotTop. Medium/heavy body. Steep roast gradient made it even lighter than the exterior would indicate. Good complexity. Steep roast gradient likely a result of the higher percentage of heat transfer via conduction.

Luis – Bright and juicy. Medium/light body and good complexity. Noted that it was sweeter than the other two.

One Response
  1. David Hunter permalink
    January 26, 2011

    I just read all four parts of home roasting coffee. It was informative and a pleasure to read. Great photographs too. I have always bought my coffee beans from places like Intelligentsia, Klatch, and most recently, Stumptown coffee. The question I have been wondering about is if home roasted coffee is truly better tasting coffee than reputable coffee roasting companies. Though I don’t have $700 to spend on a HotTop roaster, can I get great results with the popcorn popper? It seems as if the answer is, “not really”. So even though this was a wonderful experiment, I am still left wondering; should I take the plunge and start home roasting coffee myself or should I just stick with my coffee press, burr grinder, and $15 a bag roasted coffee beans?

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