Quantitative studies on roast kinetics for bioactives in coffee.

Quantitative analysis of the bioactives trigonelline (1), N-methylpyridinium (2), caffeine (3), and caffeoylquinic acids (4) in a large set of roasted Arabica (total sample size n = 113) and Robusta coffees (total sample size n = 38) revealed that the concentrations of 1 and 4 significantly correlated with the roasting color (P < 0.001, two tailed), whereas that of 2 significantly correlated inversely with the color (P < 0.001, two tailed). As dark-roasted coffees were rich in N-methylpyridinium whereas light-roasted coffees were rich in trigonelline and caffeoylquinic acids, manufacturing of roast coffees rich in all four bioactives would therefore necessitate blending of two or even more coffees of different roasting colors. Additional experiments on the migration rates during coffee brewing showed that all four bioactives were nearly quantitatively extracted in the brew (>90%) when a water volume/coffee powder ratio of >16 was used.