Flavor Characteristics and Stereochemistry of the Volatile Constituents of Greater Galangal (Alpinia Galanga Willd.)

The rhizomes of greater galangal (Alpinia galanga Willd. L.) are widely used as a spice throughout south-east Asian countries. A flavor concentrate was prepared by steam distillation under reduced pressure, and the odor character and some potent odorants of the oxygenated compound fraction that presented the characteristic odor of galanga were investigated by GCMS and aroma extract dilution analysis. Monoterpenoids of linalool and geranyl acetate, 1,8- cineole and acetoxy-I,8-cineoles, and some C6-C3 compounds of the derivatives of eugenol and chavicol were determined as important odor components. In addition, the optical purity and odor difference between the enantiomers were determined by GC and GC eluate sniffing, using a cyclodextrin column. I’ -Acetoxychavicol acetate was present in the optically active 5- configuration in the essential oil of the rhizomes. Only the (S)-enantiomer possessed the characteristic cool, woody and ginger-like odor, in contrast of no odor of the (R)-enantiomer which played an important role in the odor of the fresh rhizomes, because this compound was degraded during cooking. Among the eight isomers of acetoxy-l ,8-cineoles, (1R, 4S, 6R)- 1,3,3-trimethyl-2-oxabicyclo[2,2,2]oct-6-yl acetate (trans-2-acetoxy-l,8-cineole) which presented a woody and galanga-like odor was the most important odor constituent in the rhizomes of greater galangal.