Odorous volatiles and methoxypyrazines responsible for the musty-peanut aroma in microwave-heated sponge gourd (Luffa cylindrica)

Abstract

Microwave heating results in the generation of odorous compounds in sliced sponge gourd (Luffa cylindrica). Herein, the odorous components of microwave-heated sponge gourd were extracted, and the volatiles were separated by a solvent-assisted flavor evaporation technique. Subsequently, gas chromatography (GC)–olfactometry analysis identified 10 compounds in the aroma extract including unsaturated aliphatic aldehydes (3-hexenal; 2-octenal), alcohols (3-hexen-1-ol; 1-octen-3-ol), and ketones (1-octen-3-one; 1,5-octadien-3-one), which might be responsible for the typical green-grassy and metallic characteristics. Microwave heating could also promote the nonenzymatic browning reaction in the softened gourd to release methional and 2-acetyl-1-pyrroline, which have boiled potato and roasted-peanut odors, respectively. Furthermore, preparative GC–mass spectrometry was used to distinguish two methoxypyrazines (3,5-dimethyl-2-methoxypyrazine and 3-isopropyl-2-methoxypyrazine) responsible for a highly noticeable, unpleasant musty-peanut aroma in heated sponge gourd. Moreover, 3-isopropyl-2-methoxypyrazine might also generate an unlikeable earthy odor, resulting an off-flavor, and thus could be used as one of quality markers in sponge gourd.