Analysis of furan and monosaccharides in various coffee beans.

The furan levels in commercial coffee product samples (17 instant coffees, 12 mixed coffee, 8 canned coffee) were 49-2155, 10-201 and 15-209 ng/g, respectively. Since thermal degradation/rearrangement of carbohydrates is the main source of furan, the concentrations of furan and monosaccharides (mannose, rhamnose, glucose, galactose and arabinose) were analysed in 26 green and roasted coffee bean (Coffea arabica) varieties. In coffee beans, furan levels ranged from 4.71 (Bourbon Cerrado, Brazil) to 8.63 mg/kg (San Vicente, Honduras). Galactose was the main monosaccharide in green beans, followed by arabinose, glucose, mannose and rhamnose, on average. Roasting decreased the glucose content by about 81%, and arabinose decreased about 27% in all coffee beans. Glucose decreased the greatest after roasting and is thereby considered the major contributor to the formation of furan.