Key Odor-Active Compounds in Raw Green and Red Toona sinensis (A. Juss.) Roem. and Their Changes during Blanching

Application of aroma extract dilution analysis and headspace aroma dilution analysis revealed 51 odorants in raw green Toona sinensis and 54 odorants in raw red T. sinensis in the flavor dilution factor range of 8-4096. (E,E)-2,4-Decadienal, nonanal, 2,3,5-trimethylpyrazine, (E,Z)- and (Z,Z)-di-1-propenyl trisulfide, 2-methoxyphenol, and 4-ethylphenol were first identified as key odorants of T. sinensis. Clear differences between green and red T. sinensis in aroma profiles, flavor dilution factors, quantitative data, and odor activity values verified that (E,E)-, (E,Z)-, and (Z,Z)-di-1-propenyl disulfide, (E,E)-, (E,Z)- and (Z,Z)-di-1-propenyl trisulfide, cis- and trans-2-mercapto-3,4-dimethyl-2,3-dihydrothiophene, and dimethyl sulfide caused the distinct sulfury odor note of each variety. Further, hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, and (E,Z)-2,6-nonadienal led to the green odor note in green T. sinensis, while 2-methoxyphenol and 4-ethylphenol contributed to the intense phenolic aroma note in red T. sinensis. Quantitation experiments and triangle tests in blanched T. sinensis verified that the quick loss of the abovementioned sulfur-containing compounds, aldehydes, the alcohol (E)-2-hexen-1-ol, and phenols was responsible for the changes in the overall aroma profile during blanching.