Great question this week, as it is one that has always gnawed at me: “what do people mean by ‘bold’ coffee”?
Bold, strong, and weak are arguably some of the worst coffee descriptors because they are so vague. They could potentially refer to the roast or to the extraction. In some cases, they might be referring to both. Bold tastes can connect to the notes of origin (Sumatra, for example) or varietal (robusta, for instance). It might even be referencing the heroic actions of a comic book character. SO, allow me to explain how ‘bold’ works in these varied contexts (minus the superhero part; ‘ask lee’ is stories of origin, not origin stories).
A bold roast? This is usually synonymous with a dark roast. As outlined frequently in these dispatches, I am not a fan of the dark roast because it removes the unique flavours of origin by overriding them with the generic flavours of the roasting process: burnt, charred, and carbonized. Bold is probably one of the kinder ways to describe these basic and one-dimensional roasts. Moreover, it explains why ‘bold’ only appears in rare (but very telling) instances as a taste descriptor: steak sauce, gimmicky potato chips, grain alcohol, funky mushrooms, SUV traction control design, et al.
A bold cup? Bold in terms of brew strength is a tad more complicated. Brewing is difficult for a couple reasons. After roasting, you can only extract roughly 27-29% of the total mass. Moreover, coffee bean structure is very complex and while roasting greatly increases its solubility, water still has a tough time passing through its pores (and micropores). Hence, the two common solutions to weak coffee are to use a higher coffee-to-water ratio or to use a finer grind, which increases the surface area and amount of contact. There is a point of no return in which you ‘over-extract‘ by moving too many of the volatile flavour compounds from bean to water. The cup will become harsh, intense, dry, and bitter. Here is the point of overlap with the bold roast: flavour profiles align and it is equally generic. Any coffee when over-extracted produces these overwhelming ‘bold’ notes regardless of origin or roast.
I have outlined two routes to bad bold flavours, but would be remiss not to speak to the potentially good side of bold. Roasting is a destructive process (cellulose breaks down, sugars caramelize, acids degrade, etc). It makes beans more porous and, accordingly, brewing is easier. While based in no actual survey or study, I feel like part of the popularity of dark roasts arises from this ease of extraction. People do not actually enjoy the bold notes of roast but are attracted to the intensity of flavours. Meaning, a well-developed and well-roasted coffee brewed on the strong-end of the spectrum (just shy of over-extraction) will provide cafe guests with the ‘bold’ flavours they are seeking! And really who doesn’t want a cup that is boldly sweet, boldly clean, and boldly juicy.