Volatile profile of aromatic and non-aromatic rice cultivars using SPME/GC-MS

Authors: Bryant, Rolfe; McClung, Anna

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2010
Publication Date: 1/15/2011
Citation: Bryant, R.J., McClung, A.M. 2011. Volatile profile of aromatic and non-aromatic rice cultivars using SPME/GC-MS. Food Chemistry. 124(2):501-513.

Interpretive Summary: Rice is enjoyed by many people for its flavor and texture, especially scented rice. However, little is know about the flavor compounds of scented rice and if storage time and temperature has an affect on the flavor. The volatile profiles of nine rice cultivars was determined before and after storage using solid phase microextraction (SPME) fibers in conjunction with gas chromatography/mass spectrometer (GC-MS). This method determines the presence or absence of compounds rather than the quantity. Ninety-three volatile compounds were identified, 64 of which had not been previously reported in rice. Wide differences were found in volatile compounds of aromatic and non-aromatic rice cultivars. A number of compounds were identified that were unique to aromatic rice cultivars other than 2-acetyl-1-pyrroline, the compound that gives scented rice its popcorn flavor. However, no pattern of volatile profiles were observed that were indicative of basmati- or jasmine-derived rice cultivars. This study showed that storage time and temperature had little effect on the volatile profiles. Further research is needed to relate variation in volatile profiles with differences in quantity of these compounds and how these may impact rice flavor.

Technical Abstract: Rice (Oryza sativa L.) is enjoyed by many people as a staple food because of its flavor and texture. Some cultivars, like scented rice, are preferred over others due to their distinctive aroma and flavor. The volatile profile of rice has been explored by many investigators, some of whom have also determined a corresponding aroma using GC/Olfactometry. However, little research has been done to determine if different aromatic rice cultivars produce different flavor volatiles that would make them more desirable than others when cooked. In this study, seven aromatic and two non-aromatic cultivars were examined for their volatile profiles both before and after storage using solid phase microextraction (SPME) fibers in conjunction with gas chromatography/mass spectrometer (GC-MS). Ninety-three volatile compounds were identified, 64 of which had not been previously reported in rice. Differences were found in volatile compounds of aromatic and non-aromatic rice other than 2-acetyl-1-pyrroline (2-AP). Most of the volatile compounds were present in freshly harvested rice and rice following storage with very few new compounds being identified only after storage. Dellrose, an aromatic cultivar, and Cocodrie, a non-aromatic cultivar, had the most complex volatile profiles (over 64 volatiles). Sixteen compounds were found only in aromatic cultivars and some volatiles were found to be unique to specific aromatic cultivars. However, no distinctive pattern was observed that would identify a cultivar as being derived from Basmati, Khao Dawk Mali 105 (i.e. jasmine), or other sources of aroma. This study showed that there is a great diversity of volatiles in both aromatic and non-aromatic rice cultivars and, with further research, this may lead to a better understanding of the combination of compounds that gives a cultivar a unique flavor.