Furan, 2-methylfuran and 3-methylfuran in coffee on the Canadian market

Forty samples of commercially brewed coffee samples from 3 national chains and 48 samples of non-brewed coffee samples were collected from retail outlets located in a single Canadian city and analyzed for furan, 2-methylfuran and 3-methylfuran by headspace gas chromatography-mass spectrometry. Non-brewed samples were analyzed “as is” and some were also analyzed after brewing in the laboratory using several preparation techniques. The three analytes were detected in all samples. The rank order of concentrations for all samples was 2-methylfuran >furan > 3-methylfuran. Ground coffee types sampled included regular ground, decaffeinated and cartridge type coffee; mean furan concentrations for these coffee types were 2200, 2450 and 2360 ng/g; 9470, 10400 and 10700 ng/g for 2-methylfuran; and 447, 463 and 508 ng/g for 3-methylfuran respectively. Mean levels for both regular and decaffeinated instant coffee powders were lower with mean furan concentrations of 233 and 327 ng/g; 1600 and 1800 ng/g for 2-methylfuran and 72.9 and 75.2 ng/g for 3-methylfuran respectively. Commercially brewed coffee types sampled included regular ground, decaffeinated and espresso coffee; mean furan concentrations for these coffee types were 38.7, 53.1 and 157 ng/g; 172, 184 and 583 ng/g for 2-methylfuran; and 6.4, 6.7 and 19 ng/g for 3-methylfuran respectively. Brewing coffee samples in laboratory as per manufacturers' instructions resulted in 27-85% loss of furans-as compared to not brewed samples, loss of methyl furans exceeded that of furan by 10-15%. Brewed coffee stored/standing for up to 30 min resulted in further losses of furans, from 3 to 47%. Degree of loss was not analyte dependent but was highly influenced by storage conditions.