88A-10 |
Volatile compounds in thousand-year-old eggs |
W. S. CHAU and H. Y. Chung. Biology Dept., The Chinese Univ. of Hong Kong, Shatin, New Territories, Hong Kong, China Thousand-year-old eggs (pidans) are processed duck eggs, preserved in alkaline muddy paste or pickling solution. They are used in many Chinese dishes and can be consumed raw or cooked. Pidans, having very pungent ammonia-like flavour, are acceptable by most consumers. However, their volatile components responsible for their subtle aromas in the egg white and yolk portions have not been reported. The objectives of this research were to determine and to compare the volatile compounds in the two portions of pidan. Pidans were obtained from local supermarkets in Hong Kong. Pidan white and yolk were separated before extraction of volatile components. Extracts of volatile components were collected by simultaneous steam distillation-solvent extraction (SDE), concentrated and analysed by a gas chromatography/mass spectrometry (GC/MS). Identification and verification of each unknown component were based on comparison of the mass spectrum and retention time or retention index with that of the authentic compound. There were 60 and 76 compounds positively identified in pidan white and yolk, respectively. 40 common compounds were found in both portions. Four ketones were found only in egg white. Among them, 3-hydroxy-2-butanone had the highest peak area. Similarly, among 10 aldehydes exclusively found in yolk, decanal had the most bountiful peak area ratio. Hydrogen sulfide and acetaldehyde, which were key precursors of flavour contributing sulfur-containing compounds, were found in both pidans and cooked duck eggs in the present study and a previous one. However, some compounds, such as 3,5-dimethyl-1,2,4-trithiolane, contributing to the cooked meaty flavor of pidan, were not found in the present study. This study provides additional information on the volatile composition of pidans. The different aroma components in pidan white and yolk, based on the findings, may account for the subtle differences in aromas contained in the two portions.
Session 88A, Food Chemistry: Flavor
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