Formation of Aroma Components from Nonvolatile Precursors in Passion Fruit

Thermal treatment at native pH value during simultaneous distillation-extraction of passion fruit pulp significantly increased the concentration of a series of monoterpene hydrocarbons, alcohols, and oxides. GLC-MS investigation of a CHCl3 extract led to the identification of 3,7-dimethylocta-l,5-diene-3,7-diol, 3,7-dimethylocta-l,7-diene-3,6-diol, 3,7-dimethyloct-l-ene-3,7-diol, and 3,7-dimethyloctene-3,6,7-triol. In model experiments the role of these nonvolatile constituents as precursors of a spectrum of volatile terpenoids in passion fruit could be demonstrated. Isolation of a glycosidic fraction on a C18 reversed-phase adsorbent and following enzymatic and acid hydrolysis revealed that linalool, nerol, geraniol, and α-terpineol are not present in passion fruits in the free form but rather are present in the bound, glycosidic form. Thermal acid-catalyzed treatment liberates these monoterpene alcohols and leads to transformation into a complex spectrum of passion fruit aroma components.