One would like a chemical analysis to be able to say, in place of the cupper, whether a coffee is good. A 2013 Brazilian thesis put the question properly, and its answer is more interesting than a yes or a no.

Luisa Pereira Figueiredo, at the Federal University of Lavras, under the direction of Flávio Meira Borém, compared four arabica genotypes: Mundo Novo, widely grown in Brazil, and three belonging to the Bourbon group. Not in the laboratory, but in the field, and in three different places: Lavras and Santo Antônio do Amparo in Minas Gerais, São Sebastião da Grama in the Mogiana region of São Paulo.

First result, and it concerns place: São Sebastião da Grama proved the most promising of the three for producing specialty coffees.

Second result, and it is the one that should give pause to anyone who buys a coffee on the strength of its variety name. The three Bourbons are not equal. Bourbon Amarelo IAC J9 and the Bourbon Amarelo of SSP origin are indicated for specialty. The Bourbon Amarelo of CM origin is not, and it is not in any of the three environments. Same name, same group, and an opposite verdict whatever the terroir.

Third result, counterintuitive: caffeine content made it possible to discriminate beverage quality, and the superior coffees contained less. Sucrose and oxalic acid also proved to be good markers of quality in specialty coffees.

Fourth result, and it divides the work neatly between the plant and the place: the content of 5-CQA, a chlorogenic acid, made it possible to discriminate the environments. In other words, in this data set, chemistry is better at telling where a coffee comes from than what it is.

Two precautions, because this kind of result travels fast and badly. This is a 2013 thesis, on four genotypes and three sites. “Good coffees have less caffeine” is not a law of nature: it is a discriminating power observed in a specific sample. And nothing in it replaces a tasting; at best, it indicates where chemistry might one day assist one.

Figueiredo, Abordagem sensorial e química da expressão de genótipos de Bourbon em diferentes ambientes, doctoral thesis in food science, Universidade Federal de Lavras, 2013 (advisor Flávio Meira Borém), 127 p.