QUANTITATION OF IMPORTANT ROAST-SMELLING ODORANTS IN POPCORN BY STABLE ISOTOPE DILUTION ASSAYS AND MODEL STUDIES ON FLAVOR FORMATION DURING POPPING

摘要

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, a-acetyl-l-pyrroline (ACPY) and acetylpyrazine, were quantified in different popcorn samples. In fresh hot-air popped corn, ACTPY showed the highest concentration (437 mu g/kg), followed by ACPY (24 mu g/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 1-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.