Thermal degradation of capsaicin and dihydrocapsaicin: Mechanism and hazards of volatile products

Abstract

Food safety issues have become unprecedentedly notable. To ensure the safe use of capsaicin (CAP) and dihydrocapsaicin (DHCAP) in the food sector, their thermal degradation characteristics was examined for the first time through thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis. The second major phase occurred within the temperature range of 265–425 ℃, leading to substantial weight reductions of 96.13 % for CAP and 92.76 % for DHCAP. Thermodynamic parameters, calculated using the Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Coats–Redfern (C–R) methods, indicated that the thermal decomposition of both CAP and DHCAP was non-spontaneous and followed an F1 mechanism (−ln(1−α)). The pyrolysis of CAP and DHCAP released several volatile compounds, including CAP, DHCAP, Z-9-octadecenamide, octadecanamide, 9-decenenitrile, nonanenitrile, and 8-methylnonanoic acid. These compounds may pose certain toxicological risks and potential hazards to human health. The pyrolytic pathways for CAP and DHCAP are likely to involve the cleavage of alkyl C-N and/or amide bonds, as well as processes of deamidation and demethylation. Therefore, it is prudent to avoid heating food containing CAP and DHCAP above 265 ℃ during culinary preparation.