Mepiquat: A Process-Induced Byproduct in Roasted Cereal-Based Foodstuffs

Abstract

Mepiquat, a growth regulator widely used in agriculture, is also known as a process-induced byproduct formed in coffee from natural constituents during heat treatments such as roasting. This study examines mepiquat formation in cereal-based foodstuffs treated at sufficiently high temperature to trigger methyl transfer reactions that involve glycine betaine and choline naturally present in cereals. Color measurements of roasted barley grains revealed a correlation between thermal treatment and mepiquat content. Trials at industrial scale on instant beverages composed of roasted cereals demonstrated significant increases in mepiquat during the thermal process (in the range of 140-205 μg/kg in final products). A targeted survey of commercial products showed mepiquat in the range 69-381 μg/kg in powdered cereal instant drinks and 42-168 μg/kg in mugicha tea, a roasted barley infusion. These findings will not significantly affect the exposure of consumers to mepiquat due to the low amounts detected.

Assessing the Influence of Roasting Process Parameters on Mepiquat and Chlormequat Formation in Dark Barley Malts

“…For the MPQ formation during roasting processes, two different routes have been proposed in literature. First, in the presence of free lysine, reducing sugar and alkylating agent, a maillard-like reaction leads to the formation of MPQ (Bessaire et al 2016;Hammel et al 2014;Wermann et al 2014). The second route includes the temperature-assisted direct decarboxylation of pipecolic acid and pipecolic acid betaine leading to direct formation of MPQ and piperidine.…”

“…Color space parameters were measured using the CIE L*a*b* (CIELAB) color description system of the CIECommission Internationale de l'Eclairage (International Commission on Illumination) which is one of the most often used standards for color evaluation (Bessaire et al 2016;Lee et al 2013;Ohta and Robertson 2005). The advantage of this method lies in the fact that it utilizes three independent coordinate axes viz.…”

“…A further literature search showed that statistical probability formation of the MPQ compounds in cereals during thermal treatment below 200°C is extremely low. The MPQ formation process starts at the temperature above 200°C in cereals containing free lysine (Bessaire et al 2016). Bessaire et al (2016) showed that levels of MPQ are not correlated with a* (CieLab color space) color parameter and well correlated with L*(r 2 = 0.62) and b* (r 2 = 0.76) parameters.…”

“…Recent works established MPQ as a byproduct of the roasting process of coffee and barley grains and also correlated its presence with a change in color during roasting (Bessaire et al 2016;Hammel et al 2014;Wermann et al 2014). Maillard reaction drove the MPQ formation through to the degradation of lysine (amino acid) in the presence of trigonelline (alkaloid), conjugated with a temperature of typical roasting conditions (Hammel et al 2014).…”

“…Brewing process itself has been in focus for the presence of pesticides in beer (Bessaire et al 2016). Brewery malt is one of the basic ingredients necessary for beer production.…”