For better identification of those volatile compounds that are more odour active, ground coffee (3 g) was placed into GC headspace vials (20 mL, 22.5 mm × 75.5 mm, Sigma-Aldrich, UK). 3-Heptanone was used as internal standard (15 μL, 0.01% 3-Heptanone (Sigma, Saint Louis, USA) in methanol (Laboratory reagent grade, Fisher Scientific, UK)) to calibrate for any instrument drift.
Aroma sampling conditions were conducted according to Liu et al. (2019) (link). For GC-O nasal impact frequency (NIF) analysis, a splitter was fitted to the end of the ZB‐WAX column, and approximately half of the flow was diverted to an ‘odour sniffing port’ via a fused silica capillary passing within a heated transfer line, set at a temperature of 200 °C. Six panellists (four males and two females aged between 24 and 35 years) were used to conduct the GC-O NIF analysis. During each GC run, the panellist placed their nose close to the top of the sniffing port and recorded the time, duration and description of odours perceived (Pollien, Ott, Montigon, Baumgartner, Muñoz-Box, & Chaintreau, 1997 ). As the GC runs were 40 min long, two assessors were used to sniff each chromatogram, swapping over half‐way, to avoid fatigue.
Aroma sampling conditions were conducted according to Liu et al. (2019) (link). For GC-O nasal impact frequency (NIF) analysis, a splitter was fitted to the end of the ZB‐WAX column, and approximately half of the flow was diverted to an ‘odour sniffing port’ via a fused silica capillary passing within a heated transfer line, set at a temperature of 200 °C. Six panellists (four males and two females aged between 24 and 35 years) were used to conduct the GC-O NIF analysis. During each GC run, the panellist placed their nose close to the top of the sniffing port and recorded the time, duration and description of odours perceived (Pollien, Ott, Montigon, Baumgartner, Muñoz-Box, & Chaintreau, 1997 ). As the GC runs were 40 min long, two assessors were used to sniff each chromatogram, swapping over half‐way, to avoid fatigue.