Thermal Oxidation of 9‘-<i>cis</i>-Neoxanthin in a Model System Containing Peroxyacetic Acid Leads to the Potent Odorant β-Damascenone

The potent odorant β-damascenone was formed directly from 9‘-<i>cis</i>-neoxanthin in a model system by peroxyacetic acid oxidation and two-phase thermal degradation without the involvement of enzymatic activity. β-Damascenone formation was heavily dependent on pH (optimum at 5.0) and temperature, occurring over the two sequential phases. The first was incubation with peroxyacetic acid at 60 °C for 90 min, and the second was at above 90 °C for 20 min. Only traces of β-damascenone were formed on application of only one of the two phases. Formate and citrate solutions produced a much better environment for β-damascenone formation than acetate and phosphate. About 7 μg/L β-damascenone was formed from 5.8 mg/L 9‘-<i>cis</i>-neoxanthin under optimal experimental condition. The detailed pathway by which β-damascenone is formed remains to be elucidated. Keywords: β-Damascenone; 9‘-<i>cis</i>-neoxanthin; peroxyacetic acid; epoxide; thermolysis