A new aroma index to determine the aroma quality of roasted and ground coffee during storage

• Published in: Food technology and biotechnology 2008-10, Vol.46 (4), p.442-447
• Main Authors: Marin, Kresimir, Pozrl, Tomaz, Zlatic, Emil, Plestenjak, Andrej
• Format: Article
• Language: English
• Subjects: Analysis; aroma index; Flavor; modified atmosphere; roasted coffee; solid phase microextraction; volatile compounds
• ISSN: 1330-9862; 1334-2606

The staling of ground roasted coffee blend was studied over one year of storage. Solid phase microextraction-gas chromatography-mass spectrometry analysis was carried out to identify and semi-quantify 40 volatile compounds. We focused on volatile compounds related to the ageing of coffee: methanethiol, propanal, 2-methylfuran, 2-butanone, 2,3 butanedione, 2-furfurylthiol and hexanal. Changes in sensory properties of coffee beverage prepared from the ground roasted coffee samples during storage in laminate packages (PET/ aluminium foil/PE) under air atmosphere, under nitrogen or in punctured packages were determined. Samples were stored at (23 ± 2) °C and (40 ± 10)% relative humidity. The reference coffee was packed similarly in laminate packages under nitrogen and stored at (-20 ± 1) °C. Applying a statistical assessment of the results, we found the loss of most volatile compounds from all stored coffee samples, including even those stored under freezing conditions. The ratios of 2-methylfuran/2-butanone and methanethiol/hexanal proved useful indicators of staling. Our new proposed aroma index, the ratio of 2-furfurylthiol/ hexanal, proved to be the most effective, giving high correlation coefficients (R>_0.80) with aroma freshness for coffee brews prepared from the ground roasted coffee stored under different conditions at room temperature. Key words: roasted coffee, volatile compounds, modified atmosphere, aroma index, solid phase microextraction