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Volatile compounds characterization of aged rice using colorimetric sensor array
H. LIN (1), H. Jin (1), B. Guan (1). (1) Jiangsu university, Zhenjiang, China

Aroma of rice greatly affects palatability as well as consumer acceptability, and is one of the main factors of rice quality. Japonica rice (Wuyujing three strain) was kindly donated by farmers from Sihong Village of Jiangsu Province of PR China. After harvest, rice samples were stored in normal temperature for different storage ages (1, 3, 6 and 12 months). During storage, a number of volatile organic compounds (VOCs) changes occur, which is termed aging. In this work, total number of 120 samples (each storage age 30 samples) was used for experiment. GC-MS was primarily used to investigate the VOCs of rice samples with different storage ages.  It was found that the compounds of Benzaldehyde, 2-Fluoro-5-methylaniline increased remarkably during storage, while Hexanal, Octaethylene glycol and monododecyl ether continued to decline. According to results from GC-MS, several colorimetric dyes sensitive to VOCs of aged rice were selected. Furthermore, the mechanism of colorimetric dyes reacted to VOCs was investigated. And then, colorimetric sensor array composed of sensitive dyes were used to characterize the VOCs of aged rice. CCD camera was employed to capture the images of colorimetric sensor array before and after exposure the VOCs of rice samples. The red(R), green(G) and blue(B) components images were extracted from the images. Then, images were further optimized by image processing methods, and turning into digital data for next analysis. Principle component analysis (PCA) was employed to characterize the difference of fresh and aged rice samples. Rice samples stored with 6 and 12 months were distinguished with newly harvested rice samples through 3-dimension space PCA clusters trend. The research suggests that colorimetric sensor array was considered as an excellent method for characterization of VOCs of aged rice.

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