Headspace volatiles of sesame oil (SO) from sesame seeds roasted at 9 different conditions were analyzed by a combination of solid phase microextraction (SPME)-gas chromatography/mass spectrometry (GC/MS), electronic nose/metal oxide sensors (MOS), and electronic nose/MS. As roasting temperature increased from 213 to 247 °C, total headspace volatiles and pyrazines increased significantly (P < 0.05). Pyrazines were major volatiles in SO and furans, thiazoles, aldehydes, and alcohols were also detected. Roasting temperature was more discrimination factor than roasting time for the volatiles in SO through the principal component analysis (PCA) of SPME-GC/MS, electronic nose/MOS, and electronic nose/MS. Electronic nose/MS showed that ion fragment 52, 76, 53, and 51 amu played important roles in discriminating volatiles in SO from roasted sesame seeds, which are the major ion fragments from pyrazines, furans, and furfurals. SO roasted at 213, 230, and 247 °C were clearly differentiated from each other on the base of volatile distribution by SPME-GC/MS, electronic nose/MOS, and electronic nose/MS analyses. Practical Application: The results of this study are ready to apply for the discriminating samples using a combinational analysis of volatiles. Not only vegetable oils prepared from roasting process but also any food sample possessing volatiles could be targets for the SPME-GC/MS and electronic nose assays. Contents and types of pyrazines in sesame seed oil could be used as markers to track down the degree of roasting and oxidation during oil preparation.
The objective of this study was to analyze the pattern recognition of volatile compounds from different types of milk under LED (Light Emitting Dioxide) irradiation for 6 d. Yellow, red, blue, dark, and fluorescent light were produced using LED equipment. A mass spectrometry-based electronic nose and DFA (discriminant function analysis) were used to determine the change in volatiles from different types of milk under LED irradiation. As the LED exposure time was increased, DF1 of whole milk changed considerably under blue light, while that of skim milk changed significantly under red and yellow light irradiation. Among the types of milk tested, the most light-induced oxidation sample was LTLT milk under blue light. The volatile compounds that were shown to increase due to LED treatment in the electronic nose analysis, which was based on MS, were mainly acetaldehyde, propanal, pentanal, hexanal, heptanal, nonanal, 3-methyl butanal, 2-methyl propanal, 2butanone, 2-pentanone, 2-hexanone, and 2-heptanaone and 2-nonanone.
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