Aroma Compounds Formed from 3-Methyl-2,4-nonanedione under Photooxidative Conditions

The behavior of the prominent aroma compound 3-methyl-2,4-nonanedione under photooxidative conditions was investigated in a model experiment. The four well-known aroma compounds 2,3-butanedione, 2,3-octanedione, acetic acid, and caproic acid were identified. The main oxidation product was 3-hydroxy-3-methyl-2,4-nonanedione, an aroma compound with the odor description of rubbery, earthy, and plasticlike (GC-O). Its structure has been tentatively assigned based on mass (GC-MS) and vapor phase infrared spectra (GC-IR). The formal formation pathways are discussed for these compounds, and other origins described in the literature are presented. Keywords: Aroma compounds; 3-methyl-2,4-nonanedione; 2,3-butanedione; 2,3-octanedione; 3-hydroxy-3-methyl-2,4-nonanedione; gas chromatography−mass spectroscopy; gas chromatography−infrared spectroscopy