N,N-dimethylpiperidinium (mepiquat): Part 1. Formation in model systems and relevance to roasted food products

Abstract

This preliminary study reports for the first time the formation of N,N-dimethylpiperidinium (also termed mepiquat, a plant growth regulator used widely on cereal crops) by Maillard-driven degradation of lysine under dry thermal conditions and in the presence of the naturally occurring alkaloid trigonelline. The heat treatment was carried out at 240°C, and the resulting samples were analysed by liquid chromatography coupled to a high-resolution mass spectrometer (LC-HRMS) operating based upon Orbitrap technology. Results confirmed that lysine undergoes cyclisation by decarboxylative deamination in the presence of a carbonyl source (e.g. reducing sugars) to yield piperidine. Moreover, methyl rearrangement in the presence of trigonelline and under typical temperatures of roasting generates detectable amounts of mepiquat, identified by detailed mass fragmentation studies. The essential role of lysine in the formation of mepiquat was confirmed in a model system using ¹³C₆-lysine, which showed the expected incorporation of five ¹³C atoms into the mepiquat nitrogen heterocycle. These findings are relevant to the potential occurrence of mepiquat in roasted products such as coffee and cereals.

Keywords:

• N,N-dimethylpiperidinium
• mepiquat
• roasting
• thermal treatment
• lysine
• trigonelline
• N-methylpyridinium
• reducing sugar
• Maillard reaction