Comparison of the sensory properties of fragrant and non-fragrant rice (Oryza saliva), focusing on the role of the popcorn-like aroma compound 2-acetyl-1-pyrroline

2-Acetyl-1-pyrroline (2-AP) has been widely reported as a key contributor to the popcorn-like aroma of fragrant rice (Oryza sativa). To gain a greater understanding of its contribution to the aroma in both fragrant and nonfragrant rice, sensory profiling was conducted with a trained panel to examine the sensory properties of six boiled rice samples, three fragrant and three non-fragrant varieties. The intensity of the popcorn note as an orthonasal odour, a retronasal flavour and as an after-effect was significantly higher in fragrant rice than in nonfragrant rice. However, panellists could not differentiate these popcorn attributes between the three different fragrant rice varieties. 2-AP was extracted from the boiled rice samples by headspace solid-phase microextraction and quantified by gas chromatography-mass spectrometry. 2-AP was below the limits of quantitation in non-fragrant varieties; however, gas chromatography-olfactometry of samples indicated the presence of 2-AP in both raw fragrant and non-fragrant rice varieties.