The effect of xylose on the generation of volatiles from heated thiamine

Abstract

Isolates of volatile thermal degradation products of xylose, thiamine and xylose-thiamine mixtures were prepared by continuous steam distillation-solvent extraction, and 11, 40 and 57 components were identified, respectively, from each isolate. Pentane-2,3-dione was the most abundant component of the xylose isolate at 34% of the total volatiles. Sulphur compounds predominated in both the thiamine and xylose-thiamine isolates, with 34 and 43 representatives, respectively, being identified in each sample. Thirteen compounds are reported for the first time as thiamine thermal degradation products, and include 2-methylthiophen-3-thiol, 2-methylthiophen-4-thiol, and their 2,3-dihydro and 4,5-dihydro derivatives, three other thiophen derivatives, two alicyclic sulphur compounds and two aliphatic hydroxyketones. The addition of xylose to the model system resulted in the identification of 27 components which could not be detected from xylose or thiamine alone, and 16 (15 of which are sulphur-containing) may form as a result of xylose-thiamine interactions. They include four bicyclic structures and four alicyclic sulphur components. The presence of xylose also resulted in a 4–5-fold increase in formation of the potent meaty odour compound, 2-methylfuran-3-thiol.