Quantitation of Important Roast-Smelling Odorants in Popcorn by Stable Isotope Dilution Assays and Model Studies on Flavor Formation during Popping

Stable isotope dilution assays were developed for the quantitation of the roast-smelling popcorn odorants, 2-acetyl-tetrahydropyridine (ACTPY) and 2-propionyl-1-pyrroline (PPY). Both and, in addition, the two further roast-aroma compounds, 2-acetyl-1-pyrroline (ACPY) and acetylpyrazine, were quantified in different popcorn samples. In fresh hot-air popped com, ACTPY showed the highest concentration (437 μg/kg), followed by ACPY (24 μg/kg) which were established as the key contributors to the roasty popcorn odor. During storage of a popcorn sample for seven days in a sealed polyethylene bag, the concentrations of ACTPY, ACPY, and PPY decreased to about one third. Model studies using aqueous maize extracts and distinct precursor compounds revealed the pair proline/fructose as the most effective precursor system in ACTPY formation, while the pair l-pyrroline/2-oxopropanal was most effective in the generation of ACPY. A reaction scheme suggesting that ACPY is formed by an “acylation” of the intermediate 1-pyrroline by 2-oxopropanal is discussed.