What is trigonelline in coffee?

Trigonelline is an alkaloid found in significant concentrations in green coffee - typically around 0.5-1% of the dry weight of Arabica beans. It's the second most abundant alkaloid in coffee after caffeine and has a distinct role in shaping the flavour of roasted coffee.

During roasting, trigonelline breaks down through a process called pyrolysis, producing pyridines - a family of aromatic compounds that contribute to the roasted, nutty, and slightly smoky character of coffee. It also degrades into niacin (vitamin B3), which is one of the reasons roasted coffee is a dietary source of that vitamin.

Trigonelline itself has a bitter taste and some physiological activity, though its effects are far less pronounced than caffeine. Its significance for roasters and cuppers is mainly indirect - the roasting breakdown of trigonelline is one of the chemical processes contributing to the roasted aroma development tracked on roast curves. Light roasts retain more intact trigonelline; darker roasts have converted more of it into pyridines and niacin.