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

Nancy Chiang; Chi Tang Ho; John P. Munafo

Index: 10.1002/ffj.3446

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Abstract

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.