Identification of potent sulfur-containing odorants in scent glands of edible male giant water bug, Lethocerus indicus (Lep. and Serv.)

Giant water bug (Lethocerus indicus Lep. and Serv.) is an edible fresh water insect used for flavouring some types of Thai chili pastes and fish sauce products due to its distinctive aroma. Aroma-active compounds in the scent glands of male giant water bugs were determined by gas chromatography-olfactometry and aroma extract dilution analysis. Two trace odorants with sulfurous/catty-like and ripe guava-like odours were detected with flavour dilution factors of 729 and 9, respectively. Additional enrichment steps consisting of ultrasonic direct solvent extraction/solvent-assisted flavour evaporation combined with mercurated agarose gel chromatography enabled the identification of the compounds 3-sulfanylhexyl acetate and 3-sulfanyl-1-hexanol (tentatively identified). These sulfur-containing compounds were identified for the first time in the scent glands of male giant water bug and are thought to contribute important characteristic odours to the overall aroma of giant water bug.