Volatile compounds from dough, fermented dough, bread and popcorn: Comparison of headspace analytical methods.

摘要

Direct helium purge (DHP) was used to observe the volatile compounds from fresh bread crust, crumb and commercial flavored and non-flavored microwave popcorn. The obtained results were compared with supercritical fluid extraction (SFE) followed by DHP. Results show that the sensitivity of the latter method (SFE-DHP), in general, was several fold higher than DHP itself. Several flavor compounds reported previously in the literature using other techniques were found in this study with relatively very little sample preparation time. Previously reported high flavor dilution (FD) compounds like 2-acetyl-tetrahydropyridine, 4-vinylguaiacol, 2-phenylacetaldehyde and 2-acetyl-1-pyrroline were found by both the methods in popcorn. In popcorn, except for 2-methyl pyrazine, all the observed pyrazines were 2–6 fold higher with the SFE-DHP method. Methionol was found in bread about 10 fold higher by SFE-DHP method than by DHP method alone. SFE-DHP method showed lower abundance towards very volatile compounds due to inefficient trapping before the DHP. However, higher boiling compounds, relatively non-volatile compounds were least extracted by DHP method. The supercritical fluid (SF) extract from popcorn was also used to compare the solid-phase micro extraction (SPME) headspace technique along with injecting the SF extract directly into the gas chromatograph. SFE-SPME showed higher sensitivity towards pyrazines. Furaneol, vanillin, sulfurol, maltoxaine, and Y-nonalactone were found to be higher by the SFE-direct injection (DI) method. Direct SPME on popcorn headspace was compared with SFE-SPME. Results showed over 10 fold increase by SFE-SPME technique. Volatile compounds from several stages of breadmaking for pup straight dough (PSD) and sponge and dough (SD) methods were compared using DHP technique. Due to the increased fermentation time in the SD method, several compounds were found at higher levels than in the PSD bread crumb. 2,6-Nonadienal, 2-nonen-1-ol, E-2-nonanal and nonanal were found to be higher in the SD bread crumb. E-6-Nonenal was found only in the bread crumb by both the PSD and SD methods, with an increased level with the latter method. Proofing increased the level of acetoin in the SD method. Several furan compounds and pyrazines were found to be at higher level in the bread crust made by PSD method.