Insight of aroma in brown rice through chemical assessment of 2‐Acetyl‐1‐pyrroline (2AP) in aromatic germplasm of India

Abstract

Background and objectives Fragrance and flavor of aromatic rice are chief indicators for consumer acceptability. Aroma is evaluated by time‐consuming and labor‐intensive sensory or chemical methods. In this study, we aimed volatile profiles of aromatic rice germplasm. Findings Considering the volatile nature of aroma compounds, highly sensitive and robust gas chromatography mass spectrometry (GC‐MS) analysis is the best alternative and can accurately assess the volatile aromatic compounds. Aromatic (552) and nonaromatic (4) genotypes collected from 10 centers across the country were analyzed with GC‐MS. 2‐acetyl‐1‐pyrroline (2AP) was estimated in all the genotypes and 10 genotypes cultivated at four geographical indicator (GI) and five non‐GI centers. Full scan analysis was performed in genotypes with (22) and without (147) 2AP to identify and quantify other aroma compounds. Among the genotypes, 409 contain 2AP from 0.001 (UPRI93‐101) to 0.0478 (Jasmine Scented) ppm. The mean 2AP content was 0.009 ppm. Six more compounds were detected in full scan analysis. Of these, nonanal was highest followed by hexanal and four compounds (hydroxyl methyl furfural, indole, benzyl alcohol, and guaiacol) in similar concentration. Conclusions 2‐acetyl‐1‐pyrroline was higher in varieties cultivated at GI locations and genotype response varied from 0.66 (IR 62873‐227‐1‐16) to 2.93 (Bindli) folds. Although seven compounds (2AP and six other aroma compounds) were found, at this stage, it is premature to assign one or more of these compounds as responsible for the desired aroma considering the specificity of olfactory receptors and their highly varying odor detection threshold for individual compounds. Significance and novelty This study is first in terms of number of genotypes used, identification of aromatic rice without 2AP, and assessing impact of GI on 2AP.

Assessment of diversity of Indian aromatic rice germplasm collections for morphological, agronomical, quality traits and molecular characters to identify a core set for crop improvement

“…Applying an improved headspace solid-phase micro-extraction (HS-SPME) method combined with a GC-MS assay to a collection of 228 aromatic rice germplasm, the 2AP content in 34 genotypes was reported to be below the limit of detection (Xie et al 2019). In addition to 2AP, six volatile compounds like nonanal, hexanal, hydroxyl methyl furfural, indole, benzyl alcohol, and guaiacol were detected at similar concentration in the aromatic germplasm (Peddamma et al 2018). This suggested that it is premature to identify one or more of these compounds as responsible for the desired aroma considering the specificity of olfactory receptors and their highly varying odor detection threshold for individual compounds.…”