The Principal Flavor Components of Fenugreek (Trigonella foenum-graecum L.)

Abstract

3-Hydroxy-4,5-dimethyl-2(5H)-furanone (sotolone) was established as the character impact flavor compound of fenugreek on the basis of gas chromatography-olfactometry. Sotolone was found to occur predominantly in the (5S) enantiomeric form (95%) and to have a δ13CPDB value of-19.7‰. About 2-25 ppm sotolone were determined in fenugreek of different origins using the isotope dilution assay technique. Sotolone was generated in model systems by thermally induced oxidative deamination of 4-hydroxy-L-isoleucine (HIL) using different carbonyl compounds. Up to 24 mol% yields were obtained by boiling HIL and methylglyoxal as reactive a-dicarbonyl at pH 5 for 10 h. Strecker degradation of HIL was found to be a competitive reaction resulting in the formation of 3-hydroxy-2-methylbutanal. The lactone of HIL, 3-amino-4,5-dimethyl-3,4-dihydro-2(5H)-furanone, was found to be a better precursor of sotolone. It generated about 36 mol% sotolone in the presence of methylglyoxal.