| Abstract
| - Fructose was reacted in the presence of either cysteamine (model A) or isothiaproline (model B) inaqueous buffer at 145 °C and pH 7.0. Application of an aroma extract dilution analysis on the bulkof 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 aromacompounds was formed when isothiaproline was reacted (model B), but the flavor dilution factorswere generally lower. Substitution of the buffer by silica gel/water (9 + 1 w/w) in both models andapplication of 150 °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. Quantitativemeasurements performed by means of stable isotope dilution assays revealed a significant effect ofthe pH on odorant formation. For example, in model A, formation of 19 as well as of 11 was suppressedat pH values <5.0. A clear maximum was, however, found for 19 at pH 7.0 (∼1 mol % yield), whereas11 increased with increasing pH from 7.0 to 9.0. Keywords: Fructose; cysteamine; 5-acetyl-3,4-dihydro-2H-1,4-thiazine; N-(2-mercaptoethyl)-1,3-thiazoline; 2-acetyl-2-thiazoline; stable isotope dilution assay
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