Characterization of volatiles and identification of odor-active compounds of rocket leaves. (1st February 2018) - Raffo, Antonio
Highlights: Different volatiles show different dynamics of formation when leaves are crushed. ( Z )- and ( E )-3-hexenal, ( Z )-1, 5-octadien-3-one, contribute to green aroma notes. 4-Mercaptobutyl isothiocyanate (ITC) contributes to typical rocket aroma. 4-Methylthiobutyl ITC, 1-octen-3-one, 1-penten-3-one are other key odorants. 4-methylsulfinylbutyl ITC was detected in the headspace of crushed leaves. Abstract: The volatile profile of crushed rocket leaves ( Eruca sativa and Diplotaxis tenuifolia ) was investigated by applying Headspace Solid-Phase MicroExtraction (HS-SPME), combined with GC–MS, to an aqueous extract obtained by homogenization of rocket leaves, and stabilized by addition of CaCl2 . A detailed picture of volatile products of the lipoxygenase pathway (mainly C6-aldehydes) and of glucosinolate hydrolysis (mainly isothiocyanates), and their dynamics of formation after tissue disruption was given. Odor-active compounds of leaves were characterized by GC-Olfactometry (GC-O) and Aroma Extract Dilution Analysis (AEDA): volatile isolates obtained by HS-SPME from an aqueous extract and by Stir-Bar Sorptive Extraction (SBSE) from an ethanolic extract were analyzed. The most potent odor-active compounds fully or tentatively identified were ( Z )- and ( E )-3-hexenal, ( Z )-1, 5-octadien-3-one, responsible for green olfactory notes, along with 4-mercaptobutyl and 4-(methylthio)butyl isothiocyanate, associated with typical rocket and radish aroma. Relatively high odor potency was observed for 1-octen-3-one, ( E )-2-octenal and 1-penten-3-one.