Identification of key aroma compounds in raw and roasted lily bulbs (Bai He)

Lily bulbs (Lilium longiflorum Thunb.), known as Bai He' in Chinese, are a popular ingredient used in Asian cooking. Despite their popularity, little is known about the odorants responsible for their distinct aroma. The key aroma-active compounds present in both raw and roasted lily bulbs were isolated by solvent extraction followed by solvent-assisted flavour evaporation (SAFE) and gas chromatography-olfactometery (GC/O) analysis. A comparative aroma extract dilution analysis (cAEDA) in the flavour dilution (FD) factor range from 1 to 1024 resulted in 48 aroma-active compounds reported in L. longiflorum bulbs for the first time. The highest FD factors in raw lily bulbs were determined for (E)-hex-3-enal (green, FD 1024) and 3-methylsulfanylpropanal (cooked potato-like, FD 1024), followed by 2,2,4-trimethyl-3-oxabicyclo[2.2.2]octane (eucalyptus-like, FD 256) and 2-phenyl acetaldehyde (floral, FD 256). Following roasting, odorants with high FD values in raw lily bulbs decreased in intensity. The thermal treatment resulted in the generation of 34 aroma-active compounds. Aroma-active compounds with FD factors of 1024 in roasted lily bulbs were identified as 1-(3,4-dihydro-2H-pyrrol-5-yl)ethan-1-one (roasty), 3-methylsulfanylpropanal (cooked potato-like), 2-ethyl-3,5-dimethylpyrazine (earthy), 2,3-diethyl-5-methylpyrazine (earthy), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (maple-like), 2-ethyl-4-hydroxy-3-methyl-2H-furan-5-one (maple-like), and 2-methoxy-4-[(E)-prop-1-enyl]phenol (clove-like). In summary, the aroma-active compounds with high FD factors in raw lily bulbs decreased significantly as a result of roasting, and a new pool of aroma-active compounds were formed during the roasting process.