Identification and quantitation of key aroma compounds formed in Maillard-type reactions of fructose with cysteamine or isothiaproline (1,3-thiazolidine-2-carboxylic acid).
Fructose was reacted in the presence of either cysteamine (model A) or isothiaproline (model B) in aqueous buffer at 145 degrees C and pH 7.0. Application of an aroma extract dilution analysis on the bulk of the volatile compounds formed in model A revealed 5-acetyl-3,4-dihydro-2H-1,4-thiazine (19), N-(2-mercaptoethyl)-1,3-thiazolidine (16), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (15), and 2-acetyl-2-thiazoline (11) as the key aroma compounds among the 10 odorants detected. A similar set of aroma compounds was formed when isothiaproline was reacted (model B), but the flavor dilution factors were generally lower. Substitution of the buffer by silica gel/water (9 + 1 w/w) in both models and application of 150 degrees C for 10 min also gave the same key odorants from both thio compounds; however, under these conditions isothiaproline was the better precursor of, in particular, 19 and 11. Quantitative measurements performed by means of stable isotope dilution assays revealed a significant effect of the pH on odorant formation. For example, in model A, formation of 19 as well as of 11 was suppressed at pH values <5.0. A clear maximum was, however, found for 19 at pH 7.0 (approximately 1 mol % yield), whereas 11 increased with increasing pH from 7.0 to 9.0.
Engel
Wolfgang
W
Deutsche Forschungsanstalt für Lebensmittelchemie, Lichtenbergstrasse 4, D-85748 Garching, Germany.
Schieberle
Peter
P
D003543:Cysteamine / Q000737:chemistry*; D003903:Deuterium; D005632:Fructose / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007201:Indicator Dilution Techniques; D015416:Maillard Reaction; D013058:Mass Spectrometry; D009812:Odorants / Q000032:analysis*; D010084:Oxidation-Reduction; D014867:Water
D014867:Water; D005632:Fructose; D003543:Cysteamine; D003903:Deuterium