Abstract: The change of flavor compounds in coix seed beverage during constant-temperature storage was investigated using solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and an electronic nose system. The key flavor compounds were identified by their relative odor activity value (ROAV). Principal component analysis (PCA) and cluster analysis (CA) were applied to discriminate between samples stored for different periods. The results showed that after storage at 37 ℃ for 35 d, a total of 39 major volatile compounds were detected in coix seed beverage. The relative contents of aldehydes, alcohols, ketones, hydrocarbons and esters were increased with storage time. 1-Octen-3-ol, nonanal, 3-methylbutanal, hexanal, octanal, 2-methylbutanal, 1-pentanol, octanol and 1-hexanol, with ROAV no less than 1, were the key odor compounds of coix seed beverage during storage. The volatile compounds of aldehydes, ketones, acids and alcohols, produced from the oxidation of coix seed oil, were the main flavor components of coix seed beverage. PCA and CA could clearly distinguish between coix seed beverages with different storage times, and the PCA plot showed no overlapping between the early and mid-late stages of storage and differences in volatile compounds. By CA analysis, the samples with different storage times were discriminated effectively and classified into six clusters. Based on PCA analysis, ROAV and the changes in the relative contents of volatile compounds, nonylaldehyde, hexanal, octanal, 1-octen-3-ol were the characteristic volatile compounds causing quality deterioration of coix seed beverage during storage.

Key words: coix seed beverage, SPME-GC-MS, electronic nose, principle component analysis, cluster analysis