Changes in volatile aroma compounds of organic fragrant rice during storage under different conditions

Abstract

Background: Aroma of fragrant rice greatly affects palatability as well as consumer acceptability. Loss of desirable volatile compounds such as 2-acetyl-1-pyrroline (2-AP) and increase in volatile lipid oxidation products in aged rice have been reported. The aim of this study was to monitor the changes in key volatile compounds of organic red fragrant rice cv. Hom Daeng during storage. Effects of packaging material, storage temperature and time were evaluated using solid phase microextraction/gas chromatography/mass spectrometry.

Results: Thirteen key volatile compounds including ten lipid oxidation products were monitored. For samples vacuum packed in Nylon/LLDPE pouches at ambient temperature, significant increases in hexanal, 2-pentylfuran, 1-octanol and 4-vinyl guaiacol and significant decreases in 2-AP and geranyl acetone were found after the second month (P< or =0.05). Vacuum packing in OPP/Al/LLDPE pouches or storage at 15 degrees C better retarded the formation of volatile lipid oxidation products and greater retained desirable odorants, including 2-AP. However, accumulation of lipid oxidation products and 4-vinyl guaiacol was apparent after the sixth month under these storage conditions.

Conclusion: A greater extent and higher rate of undesirable changes in volatile compounds were found in samples stored under Nylon/LLDPE/ambient temperature condition. Nevertheless, this condition is acceptable for the retail trade of organic rice in Thailand. Storage conditions using reduced temperature or better packaging materials may be more appropriate for exported rice or superior-grade fragrant rice to better maintain the desirable rice aroma.