Volatile compounds found in expired air during eating of fresh tomatoes and in the headspace above tomatoes

Abstract Volatile compounds from tomatoes were measured in the headspace above tomatoes and in the air expired from the noses of people eating tomatoes (nosespace). Eleven target compounds, representative of the different metabolic pathways that contribute to tomato aroma were chosen for analysis. The procedure consisted of trapping volumes of headspace or nosespace on Tenax, desorbing and chromatographing the samples on gas chromatographs and quantification by integration of characteristic ion chromatograms. Small volumes (8.5 cm 3 ) of headspace were used to develop the method which was then applied to study potential sources of variation in the raw material and in the sampling procedure. The variation in headspace profiles, with time after dicing tomatoes, and with tissue maturity, demonstrated that the amounts of some volatiles changed with time and with maturity. Sampling was therefore undertaken using batches of tomatoes with similar histories and the time of sampling was fixed. The headspace and nosespace profiles from tomatoes produced raw data with substantial variation (percentage coefficient of variation 50–60%) but this appeared to be due to different amounts of voiatiles in the replicates. When data were expressed on a relative basis by normalisation, the profiles from groups of replicates were seen to be quite similar for nine of the compounds but values for 3‐methylnitrobutane and 2‐isobutylthiazole showed considerable variation. Nosespace profiles of tomato voiatiles were broadly similar between operators when expressed on a relative basis; the actual total amounts varied considerably. The headspace profiles from diced and stomached tomatoes were comparable but distinctly different from the nosespace profile. There were differences between the headspace and nosespace profiles particularly in the amounts of 3‐methylbutanal, dimethyl disulphide and hexanal which were present to a greater extent in the headspace on a relative basis.