Hydroxymethylfurfural and furfural in Coffee and related beverages. 2. Coffee

The contents of hydroxymethylfurfural (HMF) and furfural were determined in 7 series of roasted coffee with different degrees of roast. The contents first increase with increasing roasting loss (ORL) till 2-3.5 % ORL (HMF) and 2-6 % ORL (furfural), then decrease. Colombia Arabica, Kenya Robusta and an Arabica blend behave similarly, also do steamed and not steamed beans. In 21 commercial blends made of untreated (included one mocha coffee), decaffeinated, otherwise treated and natural mild coffees, values from 327 to 605 mg/kg d.b. HMF and 102 to 159 mg/kg furfural were found. In the mean, treated and mild beans contained lower levels of both substances. In the series, the HMF contents of the treated beans were slightly lower, too, but the furfural contents were rather higher than those of the untreated beans. The levels in an espresso type coffee were much lower. The contents of 11 commercial instant coffees showed great differences (0.4-4.2 g/kg HMF, 0.0-0.3 g/kg furfural). In tightly closed jars, the contents of HMF remained constant during 500 days.