Evaluation of three gas chromatography and two direct mass spectrometry techniques for aroma analysis of dried red bell peppers

Abstract

Three gas chromatography methods and two direct mass spectrometry techniques were compared for the analysis of the aroma of rehydrated diced red bell peppers. Gas chromatography methods included systems with olfactometry detection (GC–O), flame ionisation detection (GC–FID) and mass spectrometry (GC–MS). The evaluated direct mass spectrometry techniques involved atmospheric pressure chemical ionisation–time-of-flight mass spectrometry (APCI–TOFMS) and proton transfer reaction–mass spectrometry (PTR–MS). The relevance of the aroma component of the flavour was shown by sensory analysis. High intensity scores were obtained for the aroma attributes ‘bell pepper,’ ‘cooked vegetables’ and ‘grassy.’ Sixty-three volatile compounds were identified in the headspace of the bell peppers by GC–MS. According to GC–O analysis, 11 compounds possessed odour activity. Consistently across all techniques, 3-methylbutanal was the most abundant odour active compound, followed by 2-methylbutanal. Compounds present at low concentrations were more affected by the methodology. Chromatography methods correlated strongly with each other (ρ=0.946), whereas the direct mass spectrometry methods showed less significant correlation (ρ=0.613). Examining differences across all methods, it appeared that the proportions of the odour active compounds were not significantly different for GC–MS, GC–FID and PTR–MS. Significant differences were observed for APCI–TOFMS and the other techniques (P<0.01).