Quality assurance of beer and the monitoring of the brewing process are important challenges for every brewery. The vicinal diketones (VDKs) play an essential role as quality parameters in the maturation of beer and in the determination of the optimal storage time.<br/>An important representative among the VDKs is the diketone diacetyl, which causes an off-taste in beer even at relatively low concentrations. It is formed during the fermentation process, but is gradually degraded during beer aging.<br/>A major disadvantage of the analytical methods established to date is that the concentrations of diketones in beer in the range of 0.01 to 0.1 mg/l are too low for the analytical methods to be carried out directly. Therefore sample preparation using a more complex enrichment method (e.g. steam distillation, headspace GC) is required for such an analysis, which has so far practically excluded simple on-site analysis.<br/>The aim of this research project is the development of a mobile measuring unit for fast enrichment and detection of VDKs from green beer. Here we report on the use of hydrogels based on polyacryloylhydrazide (PAH) to capture diketones from beer and release them again for detection. Crosslinked polyacryloylhydrazide was synthesized by reacting polymethyl acrylate with hydrazine. The polymer was then crosslinked with diethyl malonate to form a hydrogel. The reaction of the hydrazide group with the diketones in green beer to form hydrazones and the reversibility of this bond makes this polymer system suitable for separating the diketones. Subsequent acid-catalyzed hydrolysis in a smaller volume releases the diketones in significantly higher concentration and purity for photometric determination. This makes it possible to enrich diacetyl from a beer sample in such a way that the diacetyl content can then be determined photometrically using UV/VIS spectroscopy with a detection limit of up to 0.01 mg/l.

Development of a mobile detection system in handheld format for the quantitative determination of vicinal diketones from green beer

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.