At present, there is no colorimetric method for the quantitation of the aroma compound 2-acetyl-1-pyrroline (2AP). A novel colorimetric method was developed for the determination of 2AP content using chromium hexacarbonyl (Cr(CO)6) as a reagent. The reaction of synthetic 2AP with chromium hexacarbonyl reagent solution in the presence of light produced a green product with an absorption maximum (λmax) at 623 nm. GC-MS was used to confirm the color-change reaction, which showed the loss of 2AP after the addition of Cr(CO)6. This novel method enables facile and cost-effective determination of 2AP in fragrant rice. A comparative analysis of fragrant and nonfragrant rice grain extracts showed that no color-change reaction occurred with the nonfragrant rice sample. A limit of detection (LOD) of 2.00 mg L-1 was determined by method validation with an effective linear concentration ranging from 5.00 to 60.00 mg L-1 of 2AP. The results obtained using the developed colorimetric method were consistent with those obtained by automated static headspace gas chromatography with nitrogen-phosphorus detection (SHS-GC-NPD).
Keywords: 2-Acetyl-1-pyrroline; chromium hexacarbonyl; color-change reaction; colorimetry; fragrant rice; gas chromatography–mass spectrophotometry.