Absolute contents of aroma-affecting volatiles in cooked rice determined by one-step rice cooking and volatile extraction coupled with standard-addition calibration using HS-SPME/GC-MS

Abstract

To quantify volatiles in cooked rice, analysis methods for one-step rice cooking and volatile extraction in a single headspace vial, combined with standard addition calibration using solid-phase microextraction and GC-MS were developed and applied to 41 rice varieties with various fragrances and palatability. The newly developed methods significantly improved the qualitative and quantitative recovery of volatiles compared with conventional methods. Among 29 aroma-affecting volatiles, the highest average contents (ng/g) were observed for nonanal (39.30), octanal (13.29), and 1-octen-3-ol (13.18); the total volatile contents of aldehyde, base, and alcohol groups were 4156, 2481, and 1739 ng/g, respectively. Fifteen rice varieties contained 2-acetyl-1-pyrroline in range of 41.37-421.70 ng/g. Although there were no linear correlations among volatiles and the Toyo taste-score, multivariate PLS-DA analysis of the volatile could discriminate between low- and high-palatability rice varieties. The results indicated the accuracy and practicality of the newly developed methods for quantifying volatiles in cooked rice.

Keywords: Cooked rice; HS-SPME; Quantitation; Standard addition calibration; Volatile organic compounds.