High temperature-induced alterations of volatile profiles in fragrant brown rice

Abstract

To understand high temperature-induced alterations in flavor-determining volatile property of fragrant rice, the brown rice of ‘Cheonjihyang-1-se’ was exposed to 45 °C for periods of up to 7 days and subsequent daily changes in the relative amounts of volatiles were determined by Head Space-Solid Phase Microextraction coupled with Gas Chromatography-Mass Spectrometry. Based upon their time-series patterns of quantitative changes after exposure, 66 identified volatiles were classified into the following six groups: 13 newly produced, 21 gradually increased, 5 initially increased and constantly maintained, 7 not significantly changed, 16 gradually decreased, and 4 rapidly disappeared volatiles. The amount of 2-acetyl-1-pyrroline (2AP), the most important fragrance-determining volatile in rice, rapidly decreased by 61% after 7 days exposure to 45 °C, compared with pre-exposure. Multivariate Partial Least-Squares Discriminant Analysis showed that fragrant rice exposed to high temperatures for a different day could be distinguished using their volatile profiles. These results suggest that there were significant qualitative and quantitative changes in the volatiles in brown rice exposed to unfavorably high temperatures, which may result in alterations to the flavoring and overall market quality of fragrant rice.