VOLATILE COMPOUNDS FOUND IN EXPIRED AIR DURING EATING OF FRESH TOMATOES AND IN THE HEADSPACE ABOVE TOMATOES

Volatile compounds from tomatoes were measured in the headspace above tomatoes and in the air expired from the noses of people eating tomato es (nosespace). Eleven target compounds, representative of the differe nt 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 de velop the method which was then applied to study potential sources of variation in the raw material and in the sampling procedure. The varia tion in headspace profiles, with time after dicing tomatoes, and with tissue maturity, demonstrated that the amounts of some volatiles chang ed with time and with maturity. Sampling was therefore undertaken usin g 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 variat ion 50-60%) but this appeared to be due to different amounts of volati les 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-methylnitrob utane and 2-isobutylthiazole showed considerable variation. Nosespace profiles of tomato volatiles were broadly similar between operators wh en expressed on a relative basis; the actual total amounts varied cons iderably. The headspace profiles from diced and stomached tomatoes wer e comparable but distinctly different from the nosespace profile. Ther e were differences between the headspace and nosespace profiles partic ularly in the amounts of 3-methylbutanal, dimethyl disulphide and hexa nal which were present to a greater extent in the headspace on a relat ive basis.