What is sucrose in coffee?

Sucrose is the primary sugar in green coffee beans, typically making up around 6-9% of the dry weight of Arabica green coffee (and significantly less in Robusta). It is the dominant fermentable sugar and the principal substrate for the caramelisation and Maillard reactions that develop flavour and colour during roasting.

In the green bean, sucrose accumulates during cherry maturation - ripe cherries contain more sucrose than underripe ones, which is part of why cherry ripeness at harvest has such a direct impact on cup sweetness and roast development. Higher-altitude, slower-maturing coffees tend to build higher sucrose concentrations, which contributes to their greater complexity and sweetness potential.

During roasting, sucrose begins to degrade rapidly above around 170°C. It first undergoes hydrolysis into glucose and fructose, then these simpler sugars feed both the Maillard reaction (reacting with amino acids) and caramelisation (direct thermal decomposition of sugars). By the time a coffee reaches a medium roast, most of its original sucrose has been transformed into the hundreds of aromatic compounds responsible for the flavour and aroma of roasted coffee. This is why both the quantity of sucrose in green coffee and the roast profile applied to it matter enormously for cup sweetness and complexity.