Decoding the Aroma Profile of Rice Aleurone Layer: A Molecular Sensory Approach

The rice aleurone layer contains most of the nutrients and bioactive compounds in bran. Moreover, it exhibits intense aroma characteristics due to its abundant odorants. Despite growing interest in reusing it as a food ingredient, the aroma profile of aleurone remains unexplored. This study employed solvent-assisted flavor evaporation and aroma extract dilution analysis, identifying 30 odor-active compounds within the aleurone layer. Notably, 2-acetyl-1-pyrroline (2-AP) exhibited the highest flavor dilution (FD) factor (4096). Twenty-two odorants with FD ≥ 2 were quantitated using internal standard curves. Calculations of the odor activity value (OAV) based on starch odor thresholds indicated that 13 odorants with OAVs ≥ 1. 2-AP showed the highest OAV (11948). 3-Penten-2-ol was identified for the first time in rice. The aroma recombination model achieved a high similarity with the native sample (sensory score: 2.8 out of 3). Omission tests identified 8 key odorants: 2-AP, 1-octen-3-ol, γ-nonanolactone, vanillin, 3-penten-2-ol, (E)-geranylacetone, γ-butyrolactone, and benzyl alcohol. The aleurone layer of rice exhibited a high concentration (87.2 ± 1.3 μg/kg) of 2-AP, which significantly contributes to its characteristic popcorn-like aroma. This unique aroma might be incorporated into food formulations as a natural flavor enhancer. The study provides foundational insights for optimizing flavor in aleurone-derived food products.