Determination of Carbaryl Residues in Malt and Beer and Their Impact on Beer Quality

Abstract

This work was initiated when beer from a particular brewery was found to have a harsh astringent character. Beer and brewing raw materials were analyzed for phenols, because the perceived flavor was characterized as phenolic. The analytical methods used were based on liquid chromatography with electrochemical detection. Detection of phenols and chlorophenols at the micrograms-per-liter level was achieved. Investigations showed that the suspect beer contained a component that was absent in other beers. Subsequent work showed that this component was derived from the malt and ultimately from the barley used. The component was identified as l-naphthol, which is a hydrolysis product of carbaryl (l-naphthyl methyl carbamate). Carbaryl was found in barley at concentrations as high as 5 mg/kg. Most of the carbaryl (85–90%) was lost during malting, but concentrations of up to approximately 50 μg/L l-naphthol were found in the beer produced. Beer dosed with 50 μg/L of l-naphthol was found to have the same characteristic harsh astringent flavor as the beer that initiated this investigation.