In this video, Matt Perger explains how bean-surface burning can occur during roasting and what it tastes like in the cup.
In The Coffee Roaster’s Companion, Scott Rao makes a point of amalgamating his explanations of tipping, scorching, and facing. He considers these to be more or less the same issue, with slightly different appearances. He calls the issue bean-surface burning (S Rao, 2016) He deals with these subjects collectively because the flavour taint that results from these issues is the same. They introduce burnt, ashy, and sometimes smoky flavours to the cup. Bean-surface burning means that a small section of the bean is burnt, overdevelopment means the whole thing is burnt.
An important study of roast profiling combined sensory science, mass spectrometry, and consumer surveys. Researchers found that a very fast hot roast profile, intended to achieve a scorched bean surface, and a much longer profile, intended to create a classic example of an overdeveloped roast, achieved almost identical reviews from the trained sensory panel and the consumers. Researchers also noted the predominant presence 4-ethyl-2-methoxyphenol molecule. We explore the importance of this ashy tasting VOC more in the next lesson.
This suggests that anytime you can easily see a black burn mark on the surface of a roasted bean, you can expect the burnt, smoky flavour to be present. With tipped and facing beans, this taint is blended with other tastes from the rest of the coffee bean that is not burnt.
Chipped beans, empty beans, and triangular beans are all problematic to the roaster. They are more likely to burn during roasting and will impart an ashy taint to the rest of the coffee, even if the majority of the beans are bigger and more even in size and shape.