Roast defects are basically defects that come through the flavor of the coffee due to the roasting process specifically. They are caused by the roaster. Each of these defects result in specific, unique flavors that you can identify when you cup your roast (and also a case for why you should always cup your roasts!).
There are six primary roasting defects. The first two are generally a result of too high of heat.
- Tipping: This results when it is too hot when you introduce the beans to the roaster (think back to our conversation last time on low versus high elevation beans). When this happens, hot moisture will leave the bean and burn the end. It can leave a cereal taste in the coffee. Peritus Coffee usually doesn’t have a problem with this particular issue- certain roasting machines are more subject to it than others (we use a San Franciscan roaster).
- Scorching: At the beginning of a roast, the beans are introduced to too hot an environment or too much coffee is put into the roaster at one time. It’ll put dark, burned marks on the green coffee as you check the color of the coffee throughout the roast. When you cup, you’ll get burnt, roasted, smokier flavors that come through the cup.
- Facing: This usually happens when the roaster is overloaded with too much coffee or if the roaster has the wrong drum speed when using a drum roaster (too fast or slow). The flat surface of the bean gets stuck to the side of the drum roaster and chars or burns the face of the coffee. Similar to scorching, when you cup the coffee, you’ll get a burnt, roasted, smokey taste. These flavors will be even more pronounced with lighter coffee flavors.
- Baking: This typically happens when the roast is stalled. As you roast coffee, it gets continuously warmer, but if you don’t have enough energy or heat, then the heat can’t continue to get warmer or can drop. Alternatively, if you draw out the roast super long, you’ll get some of these baking flavors as well. Unlike the first three defects, you can’t see baking on the surface of the coffee bean, but you can see it if you compare the outside color of the roasted bean and when you grind your coffee. If the colors are very similar, then there might be a baking defect. If coffee is well roasted, then the outside is much darker than the overall grind- think like a baked yellow cake with a golden outside and yellow inside. With baked coffee, the taste will be flat and dull with dry flavors and very hard and oaty like Cheerios! Baking causes a loss of acids and sugars. For espresso, sometimes you want to capture a bit of this!
- Under-development: Ever had a super acidic coffee? Underdevelopment is hard to see from the outside, but when you grind the bean, you’ll notice that the grind is significantly lighter than the outside of the bean. It is often the result of roasting too fast. The taste will be very acidic and the flavors will be in front of the palate and without much aftertaste, very one-dimensional versus complex in flavor.
- Over-development: A catch-all term for taking the roast too far. In flavor, you lose any acidity and what you do taste is very muted and flat. While most coffees have some charred characteristics, in over-developed coffees, it is quite charred.
There are a few other less common defects. Looking at these defects, it’s easy to see how some of the flavors or appearance defects overlap, but as a roaster it’s important to understand and identify the source of the defect so it can be changed in the future. Especially for a more sneaky defect like baking where the appearance might look okay, cupping is quite essential for creating consistently good coffee!