A roaster’s glossary
Coffee roasting has its own set of words and phrases that can be challenging to understand at first. Whether you’re new to roasting or need a refresh, this glossary will guide you through the keywords and definitions to help you on your journey.
Roast stages
Preheat: All roasting machines must be preheated before use so that they start every batch with the right amount of thermal energy. ROEST machines need much less time to preheat than conventional drum roasters, and their drum temperature sensors make it very easy to preheat to the correct temperature for perfect consistency.
Charge: The beginning of the roast; the moment when the green beans enter the drum.
Charge temperature: The temperature reading at the moment the beans are loaded into the drum (or “charged”). Most roasting machines only measure the air temperature at charge; with ROEST’s drum temperature sensors, you can also record the exact temperature of the drum surface.
Drying phase: The first phase of a roast. During this stage, the beans are losing moisture but there are minimal chemical reactions taking place and the beans stay greenish in color.
Yellowing: At the end of the drying phase, the beans start to turn yellow. This moment marks the beginning of the Maillard phase. ‘Yellowing’ may also simply be called ‘color change’.
Maillard phase: The second phase of a roast, sometimes also called the ‘nameless phase’. The Maillard phase begins at yellowing and continues until first crack. During this time, the beans turn brown and begin developing many of their flavors and aromas.
First Crack: The moment in the roast when beans begin to ‘pop’ for the first time. Each ‘pop’ is the result of a bean cracking open, releasing the steam and gases that have built up pressure inside the bean. The first crackmark marks the start of the development time.
Development time: The third phase of roasting, the time between first crack and the end of the roast. During this phase, the rate of chemical reactions such as Maillard reactions and caramelization increase and the flavor and color of the coffee changes rapidly.
Second Crack: After first crack, the beans begin to ‘pop’ a second time as a result of carbon dioxide pressure building up in the beans. The moment when this happens is called ‘second crack’. The ‘pops’ of second crack are usually more frequent, but higher-pitched and quieter than those of first crack. Second crack breaks open the bean cell walls, allowing coffee oils to come to the surface of the beans, which is why darker roasts sometimes look shiny. The roasting smoke becomes darker and more pungent after second crack, which is characteristic of dark roast profiles.
Drop: The end of the roast, when the beans drop into the cooling tray. Lighter roasts are usually dropped during or at the end of first crack, while the darkest roasts may continue past the end of second crack.
End temperature: The bean temperature at the end of the roast. Darker roasts typically have a higher end temperature, but very fast roasts may end at a high temperature, even though the bean color is still light.
Cooling stage: The final stage of roasting where beans are dumped into a cooling tray and blasted with cool air. Rapid cooling is essential to preserve the flavor and aroma of the roasted coffee
Roasting terms
Cupping: A standardized way of tasting roasted coffee. Cupping is used to determine the quality of green coffee when sourcing or checking for quality, as well as to evaluate the quality of a roast. Cupping may also be used to assess a coffee’s flavor profile and to come up with tasting notes to help customers understand what to expect from the coffee.
Degassing: After roasting, a lot of carbon dioxide and other gases are trapped inside the beans at high pressure. Over time, these gasses escape, a process known as ‘degassing’. Ground coffee degasses much faster than whole beans. When coffee is too fresh, the trapped gasses can make it hard to extract the full flavor of the coffee. As coffee ages further, the degassing process can start to carry away the desirable aromas of fresh coffee, leaving the beans tasting flat and stale.
Flavor profile: A description of all the aromas and tastes found in a coffee. The flavor profile of a coffee depends on how it was grown and processed at the farm, and on how it is roasted and brewed.
Maillard Reactions: A series of chemical reactions that take place in coffee beans during roasting when sugars and proteins react together. These reactions are important in developing many of the characteristic flavors and aromas of roasted coffee, as well as its brown color.
Rate of rise (RoR): Rate of rise refers to how fast a temperature reading is increasing (or decreasing). RoR can apply to any temperature reading but usually refers to the bean temperature. By observing the bean temperature RoR you can estimate how long it will take to reach the next stage of the roast. Some roasters also like to monitor the rate of rise of the air temperature (ETRoR) during roasting. Read more about Rate of rise on the blog.
Roast curve: A graph that shows how the temperatures inside the roaster change during the roasting process.
Roast profile: A set of parameters that determine how coffee beans should be, or have been, roasted.
BT: BT stands for bean temperature, usually measured by a probe in the middle of the bean pile.
ET: ET stands for ‘environmental temperature’ or ‘exhaust temperature’. Most roasting machines have one probe measuring the air temperature at some point in the process. This probe is usually positioned either inside the drum (environmental) or in the ducting passing out of the drum (exhaust).
However, the ROEST L100 Plus has both sensors: one inside the drum and one at the exhaust, so we distinguish between the air temperature sensor in the drum (ET) and the exhaust temperature sensor (ExT).
Roasting quality
Underdeveloped: Beans that didn’t ‘cook’ enough to develop their optimum flavor may be described as underdeveloped or ‘green’. In particular, this can imply that the center of the bean didn’t get enough heat. Underdeveloped beans lack sweetness and can taste like grass or straw, ‘grainy’ like cereal, vegetal and savory, or sour.
Defect: Any undesirable characteristic or flaw in roasted or green coffee beans. Systems for grading the quality of green coffee list defects to look out for and categorize them by severity. Defects in green coffee can result from improper growing, processing, and storage. Examples are quakers, beans with insect damage, or mold. Additional defects can result from roasting, such as facing or tipping.
Roasty: Describes a coffee that exhibits excessive roasted flavors. Roasty flavors are usually the result of over-roasting a coffee, but can also indicate bean-surface burning (scorching or facing). Very roasty beans may taste woody, smoky, or burned. In less severe cases, ‘roasty’ can indicate that the roast flavor overpowers the subtler flavors present in a coffee.
Tipping: Refers to the appearance of a darker spot at the very tip of coffee beans during roasting. These spots are thought to form where the embryo of the coffee bean was located. Tipping is influenced by both the characteristics of the green coffee and the roasting process: Tipping results from roasting too fast, or at excessively high temperatures, but some coffees are more prone to tipping than others.
Scorching: If the drum surface becomes too hot, it can burn the surface of the bean, leaving it with dark spots or patches. If scorching occurs, it often becomes visible early in the roast, when the drum is hottest. Scorching is of particular concern in roasters that rely on conduction to provide heat to the beans.
Facing: A different type of bean-surface burning that results from beans spending too long in contact with a hot drum wall. If the drum rotates too fast or too slow, the beans may not be well mixed and some beans may be pressed against the drum wall. These beans can then become burnt on one side (or ‘face’).
Baked: A coffee that has been roasted too slowly, at too low a temperature, or that had a drop in the rate of rise during roasting that negatively affected the flavor. Baked coffee lacks sweetness, acidity, and complexity, and tastes dull and flat. Typical flavor descriptors include cardboard or bread, and baked coffee may also develop roasty flavors.
Green beans
Green coffee beans: Unroasted coffee beans, which are bluish-green in color.
Chaff/silverskin: Green coffee beans are surrounded by a thin layer called silverskin. During roasting, the silverskin is released from the beans and blown away by the airflow in the roaster. The resulting papery waste is called chaff and must be collected and disposed of.
Coffee cherry: The coffee fruit is botanically a berry. Each fruit usually contains two seeds — the coffee beans. When ripe, coffee cherry is typically a deep red, although some varieties ripen to a yellow, orange, or pink color instead.
Pulp: The first stage of many coffee processing methods is to pass the cherries into a machine to remove the skin and most of the flesh of the fruit — together, called the pulp.
Mucilage: After removing the pulp, the beans are left with a sticky layer adhering to the parchment. This layer is called the ‘mucilage’, and may be removed by fermentation and washing, or by machine.
Cascara: Coffee pulp is generally considered a waste product and is composted. Sometimes, however, the skin and flesh of the fruit is separated and dried. Called cascara, meaning ‘husk’, these dried fruits are rich in antioxidants and caffeine and can be used to make a fruity tea-like drink.
Parchment: Inside the fruit, each seed is surrounded by a tough, papery layer called parchment. This layer is usually removed just before the beans are exported. ‘Parchment’ is also used as a general term for the beans in storage, while they still have their parchment attached.
Coffee processing: the method by which the coffee beans are removed from the coffee cherry. This will affect the coffee’s flavor and how you roast them.
Wet/Washed: The fruits are ‘pulped’, squeezing the seeds out from the fruit. The seeds are then fermented in a container to release the sticky layer that remains stuck to the seeds, called ‘mucilage’. Alternatively, the mucilage may be removed by machine. After fermentation, the beans are washed in water and then dried.
Dry/Natural: The whole fruit are slowly dried under the sun. After drying, the dried fruit flesh (called the ‘husk’ or ‘cascara’) is removed by machine.
Honey/Pulped natural: These coffees are pulped and then dried with a varying amount of the sticky mucilage layer still attached. Honey processed coffees are often differentiated by the color of the parchment i.e. yellow, red or black honey. The darker color of red or black honeys is a result of leaving more mucilage attached to the parchment, resulting in more intense fruity or fermented flavors.
Wet hulled: A traditional processing method in Indonesia, where it is called ‘Giling Basah’. The coffee is pulped and dried in a similar way to the honey process, but the drying process is stopped when the beans reach 30–40% moisture (instead of the usual 10–12%). The beans are then ‘hulled’ by removing the parchment while the beans are still moist, and the drying process then continues without the parchment attached. This process gives the coffee a characteristic earthy, full-bodied profile with low acidity.
Anaerobic/anoxic: Anaerobic or anoxic can refer to any type of process where oxygen is deliberately excluded during the fermentation step. There are many ways to create an anaerobic environment during fermentation, and the process can be applied to washed or naturally processed coffees, which means this label can refer to a number of different processing styles. For example, one producer might put whole fruit into sealed plastic bags to ferment for a day or two, and then take them out and dry them in the same way as a natural coffee. Another producer might pulp the coffee, then ferment it in sealed tanks to keep the air out, and finish the process as a washed coffee. Anaerobically processed coffees often develop very distinctive flavors, which may be floral, fruity, fermented, winey, or spice-like.
Coffee variety: Just like wine grapes might be pinot noir or cabernet, there are many varieties of coffee with different characteristics. The two main species of coffee, arabica and robusta, both have many different varieties. Common varieties of arabica include typica, bourbon and caturra.
Elevation: The height above sea level that a coffee is grown at. This has a direct impact on the size, shape, and flavor of the coffee beans, and coffee grown at higher elevations is often considered more desirable.
Country of origin: The country where the coffee is grown. Different countries will have different flavor profiles, soil types, elevations, and more. Knowing the country of origin will help you to predict what flavor profile to expect from a coffee, and how to roast it.
Single origin: Coffee that has come from a particular region in a country, or even a particular farm.
Microlot: A small amount of coffee produced in a particular way. This could be a lot of coffee from a single small farm, coffee grown on a particular part of a larger farm, or a batch of coffee processed in a particular way.
Blend: A mixture of two or more different coffees that are mixed together. A blend might consist of coffee from several countries or several lots from the same country of origin
Past crop: Coffee is a seasonal product, and most origins have a single main harvest period each year. Coffee that dates from a previous harvest season of a producing region is called ‘past crop’. Typically no longer considered fresh, though high-quality flavors can still be present in the beans.
Fresh crop: Coffee from the most recent harvest season of a producing region.
