Kathi Z’s Magic Trick The final gra

Kathi Z’s Magic Trick The final graph, Graph 4, is of a one-pound roast in a 15-kilo roaster. Kathi Zollman, roast master for New Harmony Coffee & Tea, by experimenting with PI settings, consulting Paul the engineer, and adjusting initial drop temperature, was able to get a one-pound roast to follow a pre-set profile, a feat that even the manufacturer thought
impossible. The inability to control a small fractional batch in a drum roaster has long been a problem, even for experienced roasters. To get a small batch to actually follow a large-batch profile was considered pure magic. A closer inspection reveals how the environment temperature (burner) was constantly adjusting to keep the bean temperature on the desired profile. Although this roast, like the others shown, was accomplished with a handsoff technique, it required an experienced roaster utilizing all her talents to ascertain and input the correct settings. Such things as total energy present at start of roast; energy acceleration and bleed rates; responsivity of controls; accuracy of temperature readings (bean temperature); changes in conduction and convection ratios; and the green coffee itself (hard bean, soft bean, old crop, new crop) all played a part in determining the PID settings and the desired profile. Like a good magician, Kathi just made it
look easy. (As an aside, the coffee cupped admirably as well.) Expanding the Realm of Possibilities As an industry, we are entering a time when new control technologies are becoming more widely available and cheaper. This, coupled with the exchange of information being fomented by the rise of the Roaster’s Guild, online coffee roasting bulletin boards, and more technically oriented and focused trade journals, are increasing the level of professionalism of the specialty coffee industry and expanding the realm of possibilities for those of us who have committed our livelihood, and lives, to this industry. As to the question of whether coffee roasting is art or science, it has always been both. A good roaster needs the intuition of an artist, the work ethic of a craftsman and the inquiring intellect of a scientist to truly become a master.