Part 1 – Defining ‘Best’

One of the most common questions I get is, ‘What is the best way of making coffee?’ A brilliant scientist at the turn of the nineteenth century asked—and answered—this very question. His answer not only demonstrates the expertise for which he is renowned, but it also delves into my research domain: coffee aroma chemistry. We will withhold his identity until the end of this four-part article series, by which time the reader will be able to fully appreciate his¹ contributions to coffee science.

The Question of Coffee Quality 

Coffee quality means different things to different people depending upon where they stand within the industry. Many consumers appreciate coffee for its stimulant effects. The caffeine content can be considered an objective quality marker. In contrast, the specialty coffee industry focuses on evaluating coffees based on their subjective sensory traits.   

I believe that the scientist in question was a specialty coffee connoisseur. He wrote, 

Nobody, I fancy, can be fonder of Coffee than I am; I have regularly taken it twice a day, for many years, and I certainly take care to have the very best that can be procured, and no expen[s]e is spared in making it good.

At the time he wrote those words, the stimulant properties associated with coffee’s caffeine content certainly contributed to coffee’s appeal and broadening patterns of consumption. However, the passage that follows leads me to believe that this coffee scientist did not consume coffee purely for its stimulant properties.

[W]hen Coffee is bad, when it has lost its peculiar aromatic flavour, which renders it so very agreeable to the organs of taste and of smell; it has lost its exhilarating qualities, and with them, all that was valuable in it.

One could speculate that the author associates caffeine’s stimulant effect with the coffee’s sensory qualities, but I don’t believe this to be the case. This scientist could distinguish between coffees that he liked from those that he disliked, conscientiously choosing not to consume the latter. This suggests that he knew that coffee’s stimulant effect was not linked to its sensory properties, that the caffeine content was independent of the coffee’s ‘quality’. In other words, for him, the coffee’s quality was associated with its flavour. This belief aligns with current thinking within the specialty coffee industry.

Isolating Coffee Quality from Personal Preference

Often, definitions for coffee quality become entangled with an individual’s personal preference. One might assume that the scientist’s love for high-quality coffee would prejudice his scientific judgement. Surprisingly, even in the absence of advanced scientific technology, this does not seem to be the case. He adopts a conceptual approach to the topic. He does this not by characterising the intricacies of every sensory descriptor, but rather by closely observing how coffee quality behaves. He notices, for instance, that 

[B]oiling hot water extracts from Coffee . . . an aromatic substance, of an exquisite flavour . . . this aromatic substance, which is supposed to be an oil, is extremely volatile; and is so feebly united to the water, that it escapes from it into the air with great facility.

Unlike many recent studies that focus on describing the brew — the extract that is poured into the cup — this scientist focuses on what is being lost from it.² By associating the relative coffee quality to the aroma loss, he is adopting a more objective approach that can be universally applied, independent of the coffee’s initial quality.³

In short, every thing proves that the volatile, aromatic matter, whatever it may be, that gives flavour to Coffee, is what is most valuable in it, and should be preserved with the greatest care; and that in estimating the strength, or richness of that beverage, its fragrance should be much more attended to, than either its bitterness or its astringency.

He astutely notices that

The fragrance diffused through the air is a sure indication that the Coffee has lost some of its most volatile parts; and as that liquor is found to have lost its peculiar flavour, and also its exhilarating quality, there can be no doubt but that both of these depend on the preservation of those volatile particles which escape into the air with such facility.

He understood that if the aroma was no longer present in the coffee, it must have gone somewhere else, such as elsewhere in the room, his proof being that you can smell the coffee’s aroma throughout the room as the cup quality declines.