Changes in roasted coffee aroma during storage -- influence of the packaging

Sensory investigations revealed that after 12 weeks of storage at 20°C the aroma of a bag-stored roasted coffee powder differed significantly from the reference being stored in a can. The aroma of the bag-stored coffee exhibited a clear off-flavour which was described as musty. By application of aroma extract dilution analyses and gas chromatography/olfactometry of headspace samples, 8 odourants were identified having much lower intensities in this coffee. Quantification of the 4 odour-active aldehydes, the 2 alpha-dicarbonyls and the 2 thiols showed distinct lower concentrations in the bag-stored coffee. Model experiments, in which coffee was stored under argon or oxygen, clearly showed the stabilizing effect of argon on the 8 flavour compounds, whereas oxygen led to their drastic decrease.