title: Quantitation of the intense aroma compound 3-mercapto-2-methylpentan-1-ol in raw and processed onions (Allium cepa) of different origins and in other Allium varieties using a stable isotope dilution assay.
abstract: A stable isotope dilution assay was developed for the quantitation of the potent onion odorant 3-mercapto-2-methylpentan-1-ol (1) using mass chromatography and synthesized [(2)H(2)]-3-mercapto-2-methylpentan-1-ol as the internal standard. Application of the newly developed method on onions from different origins revealed amounts between 8 and 32 microg/kg in raw onions, whereas 34-246 microg was found in sliced, stored (50 min), and then cooked onions. In extracts prepared by simultaneous steam distillation-extraction the highest concentrations of 1 were formed, amounting to >1200 microg/kg. The much higher content of 3-mercapto-2-methylpentan-1-ol in cooked onions suggested its formation from specific, yet unkown, precursors enzymatically formed during cutting of raw onions. 1 was for the first time identified and also quantified in other Allium species such as chives, scallions, and leek, whereas surprisingly garlic and bear's garlic did not contain the aroma compound.
authors.affiliation: Institut für Lebensmittelchemie der Technischen Universität München, Lichtenbergstrasse 4, D-85748 Garching, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Granvogl
authors.forename: Monika
authors.initials: M
authors.lastname: Christlbauer
authors.forename: Peter
authors.initials: P
authors.lastname: Schieberle
mesh_terms: D000490:Allium / Q000737:chemistry*; D003903:Deuterium; D008401:Gas Chromatography-Mass Spectrometry; D007201:Indicator Dilution Techniques; D009812:Odorants / Q000032:analysis*; D000439:Pentanols / Q000032:analysis*; D013438:Sulfhydryl Compounds / Q000032:analysis*
chemical_list: D000439:Pentanols; D013438:Sulfhydryl Compounds; C406689:3-mercapto-2-methylpentan-1-ol; D003903:Deuterium