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

Adam Ekielski,Pawan Kumar Mishra,Tomasz Żelaziński

doi:10.1007/s11947-018-2087-4

Adam Ekielski, Pawan Kumar Mishra + Show 1 more

Open Access

https://doi.org/10.1007/s11947-018-2087-4

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Abstract

The aim of this work was to examine the effect of temperature and time on mepiquat and chlormequat pesticides’ formation during the barley malt roasting process. The study was conducted for roasting of green malt and kilned malt. The barley used for the study was of the ecological type and verified by us to be free of any quaternary ammonium pesticides. In our study, we observed the formation of chloromequat (CHLM) along with mepiquat (MPQ). Both the compounds share the similarity in quaternary ammonium structure but to the best of our knowledge, it is the first report where CHLM formation has been observed during the roasting process. Additionally, we tried to study the effect of processing parameters (temperature and time) on the quantity of MPQ and CHLM formed during the process, using response surface methods. Additionally, the effect of process parameters (time and temperature) on the color parameter of luminosity (L*) values was also studied using the response surface methodology. The key factor which determined the amount of compounds produced in the course of roasting was found to be temperature; on the other hand, duration of roasting was observed to be of lesser effect. In the process of roasting dry malt, the CHLM presence was detected at a temperature above 433 K (160 °C), while the MPQ content was found to be present at a temperature above 442 K (169 °C). In the case of green malt, the temperature at CHLM and MPQ content was detected and was found to be higher than kilned malt. We also observed that CHLM formed at lower temperatures and shorter roasting time as compared to MPQ.

Highlights

Chlormequat (CHLM) and mepiquat (MPQ) are common quaternary ammonium pesticides used as plant growth regulators
We report the formation of CHLM along with MPQ during the malt roasting process and tried it to find the optimal condition of processing parameters for the quantity of pesticide formed using response surface methodology
L* color parameter of roasted products has already been correlated with the quantity of acrylamide and MPQ and results have already been reported, where these products were proposed to be formed via Maillard reaction (Bessaire et al 2016; Mizukami et al 2016, 2014)

Summary

Introduction

Chlormequat (CHLM) and mepiquat (MPQ) are common quaternary ammonium pesticides used as plant growth regulators. In addition to MPQ, melanoidins have been reported to be formed by Maillard-like reactions during the roasting process of Barley and coffee (Bekedam et al 2008; Moreira et al 2012; Papetti et al 2006) These melanoidins are responsible for color changes during the roasting process (Papetti et al 2006). A close connection between product color changes and MPQ formation can be assumed From these facts, we can infer that higher roasting temperature generated higher MPQ content in roasted products as the consequence of nonenzymatic browning reaction.

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