Synthesis and pyrolysis of ethyl maltol ester

Abstract

Ethyl maltol is one of the most important aromatic components in food and cigarettes because of its caramel flavour. However, the development of ethyl maltol is limited by problems such as heavy smell, low threshold, strong volatility and poor stability. In order to develop a new class of high-temperature resistance and caramel flavours for cigarettes, eight new ethyl maltol flavours were synthesized using the reaction of ethyl maltol with a carboxylic acid. The target compounds were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), infrared spectroscopy (IR) and high-resolution mass spectrometry (HRMS). By gas chromatography–mass spectrometry-olfactometer (GC–MS-O), the aroma characteristics of esters were evaluated. Four compounds with strong aroma were conducted with thermogravimetry (TG), derivative thermogravimetry (DTG) and pyrolysis-gas chromatography/mass spectrometry (Py–GC/MS) to analyse their heating stability. TG–DTG results showed that the degradation temperature of ethyl maltol esters was significantly higher than that of ethyl maltol, which could effectively slow down the volatilization of ethyl maltol. Py-GC/MS results showed that a large amount of ethyl maltol and many esters with aroma were formed during thermal degradation of the four compounds at 300°C, 350°C and 400°C. The above results show that the esterification of ethyl maltol was a good strategy to slow release flavours, and ethyl maltol ester latent aroma compounds have significant applications in high-temperature processed food and tobacco. This work may provide a new method to improve the stability of spices and expand their multifunctional application.