Quality reduction of beer stored in transfer tubes of a dispensing system – an investigation with sensory and GC/MS analyses

Dispensing systems are essential in the beer supply chain and form one of the last steps to its final link – the consumer. The maintenance and hygiene of dispensing systems are crucial as they influence the beer quality directly. Dispensing systems comprise various equipment and components necessary to pour a beer in the quality desired by the brewer. The key components with the most prominent product contact are beer transfer tubes. Depending on the construction properties of a gastronomy’s premises, long distances have to be covered frequently, resulting in significant filling volumes. For decades, brewers, sommeliers and connoisseurs have known that long hold-back times of beer in the beer tubes reduces quality. In such a case, discarding the whole beer tube’s volume is necessary before serving the first tapped beer to meet the quality standards of brewers, gastronomers, and consumers. This study investigates sensory and analytically aroma changes of three different beer styles during storage in a beer transfer tube. For this purpose, an experimental dispensing system with six beer hoses was constructed. The beer storage in the transfer tubes was conducted at two different temperatures, 5 °C and 20 °C. After particular time intervals, the beer was poured and analysed for aging indicators, flavours by GC/MS resp and a trained tasting panel. The results show significant influences on the aroma profile after three hours of storage. The panel identified a change in the aroma profile to flavours usually associated with oxidation and aging. In the comparison of the two storage temperatures, higher temperatures significantly worsen the aroma profile. These findings were supported by an increase in aging indicators determined by GC/MS analysis.