Development of a stable isotope dilution assay for the quantification of 5-methyl-(E)-2-hepten-4-one: application to hazelnut oils and hazelnuts.
A stable isotope dilution assay was developed for the quantitation of the hazelnut odorant 5-methyl-(E)-2-hepten-4-one by mass chromatography using synthesized [(2)H](2)-5-methyl-(E)-2-hepten-4-one as the internal standard. Application of the method on two batches of commercial hazelnut oils, processed from either roasted or unroasted nuts, revealed 6.4 microg 5-methyl-(E)-2-hepten-4-one per kg of unroasted oil whereas 315.8 microg per kg was determined in the roasted nut oil. The about 50-fold higher amount of 5-methyl-(E)-2-hepten-4-one in roasted hazelnut oil suggested the necessity of a thermal treatment to generate the flavor compound. Pan frying of raw hazelnuts (9 to 15 min) or boiling of the crushed nut material for 1 h in water led to an increase of 5-methyl-(E)-2-hepten-4-one by factors of 600 and 800, respectively, thereby corroborating that the major part of the nut flavorant is formed during heat treatment from a yet unknown precursor in hazelnuts.
Pfnuer
P
P
Institut für Lebensmittelchemie der Technischen Universität München, Deutsche Forschungsanstalt für Lebensmittelchemie, Garching, Germany.
Matsui
T
T
Grosch
W
W
Guth
H
H
Hofmann
T
T
Schieberle
P
P
D000475:Alkenes / Q000032:analysis* / Q000138:chemical synthesis; D003903:Deuterium; D005511:Food Handling; D007553:Isotope Labeling / Q000379:methods; D007659:Ketones / Q000032:analysis* / Q000138:chemical synthesis; D009754:Nuts / Q000737:chemistry*; D010938:Plant Oils / Q000737:chemistry*
D000475:Alkenes; D007659:Ketones; D010938:Plant Oils; C412086:5-methyl-2-hepten-4-one; D003903:Deuterium