Isolation and identification of a novel Maillard pigment, beer-furpipate, from dark beer.

Beer color is primarily formed through the Maillard reaction. Our research focused on identifying low-molecular-weight pigments in beer, which led to the detection of an unidentified pigment (X) with an absorption maximum at around 400 nm in the basic fraction of beer samples. We found that the amount of compound X increased more than 30 times when fructose was added to dark beer and subsequently autoclaved. We successfully isolated compound X from 10 L of the heated beer using various chromatographic procedures. The mass spectrometry showed that the molecular formula of compound X is C16H17O4N. The nuclear magnetic resonance (NMR) spectrum analyses indicated that compound X is (5-{(E)-[2-(5-hydroxymethylfuran-2-yl)-5,6-dihydropyridin-3(4H)-ylidene]methyl}furan-2-yl) methanol. Since this yellow pigment is a novel Maillard reaction product and a derivative of furpipates, we named it beer-furpipate. Pale and dark beers contain about 0.06 μg/mL and 0.18 μg/mL of this pigment, respectively.