Thermal decomposition study of menthyl-glycoside by TGA/SDTA, DSC and simultaneous Py-GC–MS analysis

Abstract

To develop thermal stable flavor, a glycosidic bond flavor precursor of menthyl-β- d-glucopyranoside (MGLY) was synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the glycoside were investigated by thermo-gravimetric and simultaneously differential thermal analysis (TGA/SDTA), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography–mass spectroscopy (Py-GC–MS). TGA/SDTA gave the TG–DTG and DTA curves simultaneously, the TG–DTG curve showed the T p of MGLY was 298.9 °C with a largest weight loss rate, the total weight loss was 94.4%. The DTA curve illustrated an endothermic peak at 297.5 °C. The T peak of MGLY measured by DSC was 291.0 °C. Py-GC–MS was used for the qualitative and semi-quantitative analysis of the pyrolysis products at 200, 300, and 400 °C. The results indicated that: (1) There was little MGLY degradation at 200 °C with the increase of temperature, a large amount of menthol and few by-products were produced at 300 °C, the by-products were significantly increased at 400 °C. (2) The characteristic pyrolysis product was menthol. It showed the primary decomposition reaction was the cleavage of O-glycosidic bond of the glycoside, 300 °C was an optimized temperature for MGLY to release the specific flavor of menthol. The study on the thermal behavior and pyrolysis products of the MGLY would make it possible that this kind of flavor precursors was used to provide the product specific flavor during heating process.