Automated Profiling Software

While data-logging software tracks roasts but does not control a roaster, automated profiling software tracks and controls roasts via a feedback loop. These programs attempt to follow a “model” roast profile by controlling the gas and airflow during a roast. Whenever a roast does not track the model curve exactly, the software makes tiny adjustments, as often as multiple times per second, to stay on the curve. Profiling software works like a person driving a car: No one steers perfectly straight ahead; instead, one makes frequent microadjustments to steer as straight as possible.

While a well-designed automated system could theoretically roast more consistently than any human could, most of the systems on the market today do a poor job of reliably replicating roasting results. Despite sales departments’ claims to the contrary, no off-the-shelf roasting software will keep your roast pinned to the intended profile every batch, at least not without some tricks that compromise coffee flavor. Often, when a batch drifts a little off course, software overreacts by drastically

changing the gas setting or exhaust fan RPM to stay on profile. In such a batch, the software may successfully track the profile, but the result in the cup will differ from what one would expect from the model profile.

You might not want to roast using automated profiling software, but if you can afford it, you might consider buying the software for purposes other than controlling roasts. Allowing the software to manage a roaster during the initial warm-up, between batches, and during the cool-down at the end of a roast session frees the machine operator to tend to other tasks, thereby increasing productivity. Depending on the software’s proficiency, you might feel comfortable allowing it to manage certain phases of some roasts. Roast-profiling software also usefully catalogs past batches and profiles for future reference.

A Japer with an afterburner (The afterburner is the stainless steel cylinder at the top left)

When buying a roasting machine, you must decide whether you need a pollution-control device. Roasters most commonly use afterburners and occasionally use electrostatic precipitators or wet scrubbers.

Coffee roasting produces a long list of nasty emissions, many of which are carcinogenic, including volatile organic compounds, aldehydes, nitrogen compounds, sulfur compounds, and carbon monoxide. The particulate matter in smoke from roasters contributes to air pollution, and the odor of the emissions often bothers neighbors. Most jurisdictions do not require small roasters to use pollution-control devices, but without one, a roaster may run into problems with neighbors who file

“nuisance complaints” about the roaster’s smoke and smell. I had a long, stressful, and expensive conflict with the neighbors of my first roastery, even though I was roasting only 20 lb batches for 10 hours per week in the business district of a small town. My advice is to do your homework, find out what your local government requires, and try to figure out what your neighbors will accept before you install a roaster. A little research ahead of time may save you a lot of headaches later.

Roasters have two main choices of afterburner: thermal oxidizer or catalytic oxidizer. A thermal oxidizer heats a roaster’s exhaust gases to approximately 1400°F (760°C) and retains the air for at least 0.4 second. It does a great job of eliminating smoke, volatile organic compounds, and odors but consumes a tremendous amount of fuel, often twice as much as its associated roasting machine. Catalytic oxidizers use a precious-metal catalyst that reacts with volatile organic compounds to produce CO₂ and water. The catalyst accelerates the reactions, allowing them to occur at lower temperatures. Catalytic oxidizers use less fuel than thermal oxidizers do, but they require periodic replacement of the catalyst and frequent cleaning to prevent back pressure that interferes with the roaster’s airflow.

I’ve personally owned a pollution-control system consisting of a wet scrubber, electrostatic precipitator, and large box containing 500 lb of carbon pellets to absorb odors. Scrubbers and precipitators each remove particulate and odors from the air, and the carbon absorbs odors. While it’s possible that those technologies have improved since my unpleasant experiences with them, I found they required a lot of cleaning and maintenance, created variable back pressure at the roaster, and were not as effective as an afterburner. If you buy a pollution-control device, I recommend sticking with the time-tested afterburner.

I’ve offered this book in hopes of helping roasters avoid some of the frustrations I experienced While learning to roast. I’d like the reader to View my recommendations as a set of successful methods learned over two decades of varied experience, not as a static system of rules.

While there are many legitimate approaches to roasting coffee, our industry has, until now, had little open discussion of a systematic approach. I hope, at the least, that this book is the beginning of that discussion.

Afterburner A device that heats the exhaust air from a roaster in order to destroy particulate andodors.

Alkaloid Any of a group of organic, nitrogenous compounds that are physiologically active andusually bitter.

Aroma A quality that can be detected by the olfactory system.Astringent Causing the mouth to pucker or feel dry upon ingestion.

Baked A roast defect that reduces coffee’s sweetness and creates flat, papery, cereal-like flavors.

Caramelization A complex series of sugar-browning reactions that creates numerous newcompounds.

Carbonization The formation of carbon from an organic substance by pyrolysis.

Catalytic oxidizer An afterburner that uses a precious-metal catalyst to clean roasting exhaust atrelatively low temperatures.

Cellulose A polysaccharide that is the main constituent of plant cell walls.

Chaff (silver skin) Part of the husk of the coffee seed (bean); released as beans expand duringroasting.

Charge To load beans into the roasting chamber of a coffee-roasting machine.

Charge temperature The air temperature in an empty roasting machine just before a batch is loaded.

Chlorogenic acid A polyphenol and antioxidant found in high concentration in coffee beans.

Cinnamon roast The lightest commercial roast; produced by dropping the beans during early firstcrack.

City roast A light roast, terminated during the latter stages of, or just after, first crack.

Coffea arabica The most widely planted and highest-quality commercial species of coffee plant,native to Ethiopia.

Coffea robusta (Coffea canephora) A hardy, but low-quality, commercial species of coffee plantnative to sub-Saharan Africa. Robusta is the second-most-planted coffee species and yields coffee with approximately double the caffeine of arabica coffee.

Coffee-roasting machine A specialized oven that transfers heat to coffee beans in a stream of hot gaswhile continually mixing the beans to ensure they roast evenly.

Conduction The transfer of heat from one substance to another by direct contact.

Continuous roaster A high-yield roaster in which axial position, not time, determines beantemperature. Such roasters receive, roast, and discharge beans in a constant stream, as opposed to in batches.

Creosote A brown, oily liquid mixture of phenols and other organic compounds deposited in theexhaust ductwork of a coffee roaster.

Dark roast A smoky, bitter roast produced by discharging beans after the onset of second crack.

Development The degree of breakdown of a roasted coffee bean’s cellulose structure.

Double drum A coffee-roasting machine with a drum made of two concentric layers of metalseparated by a gap several millimeters wide.

Drum roaster A coffee-roasting machine in which the beans are tumbled in a rotating, cylindricaldrum.

Electrostatic precipitator A device that removes particulates from coffee-roasting exhaust by using ahigh-voltage electrostatic charge to cause the particles to stick to charged panels.

Endothermic flash A phenomenon during first crack in which the release of water vapor from theinner beans causes the beans’ surface temperatures to suddenly cool.

Ferment A green-coffee defect that is the result of chemical breakdown by microbes.

First crack A phase of coffee roasting characterized by loud, popping noises created by the releaseof pressure and water vapor from the inner beans.

Fluid-bed roaster A drumless coffee-roasting machine in which beans are rotated and held aloft by astream of hot gases.

French roast A dark, bittersweet roast produced by dropping a batch after oils begin to bleed fromthe bean surfaces.

Full city roast A medium roast dropped just before, or just after, the onset of second crack.

GrainPro A brand of hermetically sealed bags for storing agricultural products such as coffee beans.

High-yield roaster A very fast coffee-roasting machine that preserves an unusually high proportion ofcoffee’s moisture and organic matter.

Italian roast The darkest commercial roast, Which produces bitter, pungent, acrid coffee.

Light roast A roast level produced by dropping beans before, or just after, the end of first crack.Cinnamon and city roasts are light roasts.

Maillard reactions Chemical reactions between amino acids and reducing sugars that contribute tocoffee’s brown color and roasty flavors.

Medium roast A roast dropped just before or just after the onset of second crack. Full city andViennese are medium roasts.

Radiant In coffee roasting, a term describing the transfer of heat from one body to another in closeproximity.

Rate of rise (ROR) The progression of bean temperature per unit time during a roast.

Reducing sugars In coffee roasting, sugars that donate electrons When reacting with amino acids inMaillard reactions.

Refractometer A device used to measure the refractive index of a solution. A coffee’s refractiveindex directly relates to its density and concentration.

Roast profile A graphical representation of the progression of bean-probe temperature readingsduring a roast.

Second crack A phase during a dark roast in which the release of C02 from the beans creates loud,popping noises.

Specialty coffee Any reference to coffee, or the coffee business, related to the use of higher-qualityarabica coffee beans.

Stack effect The movement of air out of a chimney due to differences in air density.

Temperature gradient During roasting, the difference in temperature between a bean’s core and itssurface.

Thermometric lag The delay in a thermocouple’s measurement of a substance’s temperature.

Trigonelline A bitter alkaloid found in coffee; the methyl betaine of nicotinic acid.

Trowel A small scoop mounted in the faceplate of a coffee roaster for sampling beans during roasting.

Underdeveloped A term describing a part of a coffee bean’s structure not sufficiently broken downby roasting.

Vacuum sealing A packaging method involving the removal of air before sealing.

Viennese roast A medium-dark roast produced by dropping beans just after the bleeding of oils frombean surfaces.

Volatile aromatic compounds Soluble gases that contribute to the aroma of coffee.

Water activity (a_w) The partial vapor pressure of water in a substance divided by the standard statepartial vapor pressure of water.

Wet scrubber A device that passes a roaster’s exhaust air through a spray of water to remove odorsand particulates.

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Scott Rao has owned and operated cafes and has roasted coffee since 1994. When not writing books about coffee making, he does freelance consulting, specializing in coffee roasting and cafe startups. You can contact him at scottrao@gmail.com.

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