|OBANDO-ULLAO, JAVIER - Costa Rican Institute For Research And Education On Nutrition And Health(INCIENSA)|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2022
Publication Date: N/A
Interpretive Summary: Whole rice and varieties with colorful bran offer consumers proven health-benefits. Two USDA long-grain rice varieties, and two others varieties that offer health-promoting capacity due to their unique germplasm were selected to study. These varieties have been characterized agronomically and/or with regard to phenolics and anthocyanin compounds but, not for volatiles. Besides the most important volatile in aromatic rice, 2-acetyl-1-pyrroline, there are well over 100 other aroma compounds in the literature across a wide range of aromatic and/or colorful bran rice varieties. Researchers have begun working with several novel and/or new rice varieties to develop value-added beverages, flours, freeze dried powders and health-promoting foods. We are interested in exploring the endogenous rice volatiles immediately after de-hulling, to differentiating possible volatile contributions from freshly prepared whole kernels, bran and flours. Four previously uncharacterized varieties (Rondo, Cahokia, Scarlett Tiara) were chosen to obtain volatile baselines that will be used to explore changes resulting from rice germination and processing during value-added product development. To the best of our knowledge, this is the first GC-MS volatiles report in Rondo, Cahokia, Scarlett and Tiara. Of the three colored-bran varieties, the purple rice Tiara delivered some of the highest compound levels for key aroma-impact volatiles known in rice, especially those varieties with colorful bran. For example, heptanal, 2-acetyl-1-pyrroline, benzaldehyde, guaiacol (2-methoxy phenol) and total compounds were significantly higher in Tiara, and benzothiazole had the significantly highest levels in Tiara and IAC600 compared to Scarlett, and the brown varieties. Cahokia high-protein rice delivered a surprisingly high volatile load, however, several compounds fell into classes that indicate oxidation and/or sensory issues if concentrations are excessive. Cahokia displayed the highest significant volatile compound levels reported in the analysis for hexanal, 2-heptanone, 1-heptanol, 1-octen-3-ol, octanal, (E)-2-octenal, 1-octanol, nonanal and total volatiles. Several other compounds were tentatively identified that might be of interest since they have pleasant fragrances. A more in-depth analysis and compound confirmation with standards is underway, to ultimately deliver a more comprehensive review of these data and trends.
Technical Abstract: A selection of varieties of long-grain rice have appeared recently that offer health-promoting capacity due to their unique germplasm (anthocyanin-rich, and high-protein). These varieties have been characterized agronomically and/or with regard to phenolic compounds but, not for volatiles. To the best of our knowledge, this is the first report of GC-MS volatiles recovered in Rondo (an organic rice used for beverages), Cahokia (a high protein brown rice), two new germplasm releases from the USDA: Scarlett (red) and Tiara (purple) rice. Tiara delivered some of the highest levels for four key aroma-impact volatiles known in rice, especially those varieties with colorful bran. Cahokia delivered a surprisingly high volatile load, however, several compounds fell into classes that indicate oxidation and/or sensory issues if concentrations are excessive. Two new USDA germplasm releases (Scarlett red rice and Tiara purple rice) were preliminarily characterized for aroma volatiles. A newly marketed high protein brown rice (Cahokia) as well as a brown rice often utilized for beverage production (Rondo) were also characterized. These varieties need baseline volatiles determined for gauging future sensory changes during value-added product development.