Headspace volatile composition and oxidative storage stability of pressed marama bean (Tylosema esculentum) oil

Indication of the color change on the oxidation properties of fragrant rapeseed oil during shelf storage

The cause and trend of color change and their links to oxidative properties were investigated by simulating shelf storage conditions for fragrant rapeseed oils (FROs). Under illumination, the L* value gradually increased with the storage time. The a* and b* values showed different trends depending on brands. The photodegradation rates of chlorophylls were 8.6 ∼ 15 times higher than those of carotenoids. The change in color of FROs was mainly caused by the light-induced photodegradation of chlorophyll. Compared with the hydroperoxides, the contents of some secondary oxidation products [i.e., 2-butenal, octane, (Z)-2-octene, 2,4-octadiene, (Z)-2-heptenal, (E, E)-2,4-heptadienal, and (E)-2-decenal] were more closely associated with the color variation with correlation coefficients of 0.6 ∼ 0.94. Significant negative correlation was found between α-tocopherol content and oil color difference. Therefore, illumination was the main reason for the color degradation of the FROs. The varying degree of color difference was strongly linked to the quality deterioration caused by oxidation.

Characterization of Key Odorants in Scallion Pancake and Investigation on Their Changes during Storage

To characterize key odorants in scallion pancake (SP), volatiles were extracted by solvent extraction-solvent assisted flavor evaporation. A total of 51 odor-active compounds were identified by gas chromatography-olfactometry (GC-O) and chromatography–mass spectrometry (GC-MS). (Z/E)-3,6-Diethyl-1,2,4,5-tetrathiane was detected for the first time in scallion food. Application of aroma extract dilution analysis to extracts showed maltol, methyl propyl disulfide, dipropyl disulfide and 2-pentylfuran had the highest flavor dilution (FD) factor of 4096. Twenty-three odorants with FD factors ≥ 8 were quantitated, and their odor active values (OAVs) were calculated. Ten compounds with OAVs ≥ 1 were determined as the key odorants; a recombinate model prepared from the key odorants, including (E,E)-2,4-decadienal, dimethyl trisulfide, methyl propyl disulfide, hexanal, dipropyl trisulfide, maltol, acetoin, 2-methylnaphthalene, 2-pentylfuran and 2(5H)-furanone, successfully simulated the overall aroma profile of SP. The changes in odorants during storage were investigated further. With increasing concentrations and OAVs during storage, hexanal became an off-flavor compound.