Characterization and discrimination of premium-quality, waxy, and black-pigmented rice based on odor-active compounds.

Background: Odor-active compounds have been studied in cooked aromatic rice, but not in specialty rice types that have distinctly different flavors. We analyzed the odor-active compounds emanating from three different types of specialty rice (premium-quality, waxy and black-pigmented) and identified the differences in odor-active compounds among them.

Results: Twenty-one, 21 and 23 odorants were detected using GC-O for cooked samples of premium-quality, waxy and black-pigmented rice cultivars, respectively. Hexanal was the main odorant in premium-quality and waxy cultivars; however, waxy cultivars had 16 times higher hexanal odor activity values (OAVs) than premium-quality cultivars, indicating premium-quality rice had a less pronounced overall aroma. 2-Acetyl-1-pyrroline was the main contributor to overall aroma in black-pigmented rice, followed by guaiacol. The three types of specialty rice were clearly discriminated based on the OAVs of their odor-active compounds using multivariate analyses. Six odor-active compounds [2-acetyl-1-pyrroline, guaiacol, hexanal, (E)-2-nonenal, octanal and heptanal] contributed the most in discriminating the three types of specialty rice. Six very similar superior cultivars of premium rice could likewise be readily separated using aroma chemistry.

Conclusion: The ability to discriminate the aroma among rice types using the OAVs of the principal odor-active compounds facilitates our understanding of the aroma chemistry of specialty rice.