Monitoring of metabolites and by-products in a down-scaled industrial lager beer fermentation

Abstract: The sugar composition of the wort and how these sugars are utilised by the yeast affects the organoleptic properties of the beer. To monitor the saccharides in the wort before inoculation and during fermentation is important in modern brewing industry. Reducing the duration of the brewing process is valuable and can be achieved by reducing the fermentation time by an increase in temperature. However, this must be done without changing the quality and characteristics of the end product, another incitement for proper monitoring of the wort. During fermentation, brewer´s yeast produces various by-products that affect the flavour in beer. The temperature has been reported to affect the metabolism of such compounds. In the present thesis work, monitoring with high performance chromatography of individual saccharides and ethanol was performed during a down-scaled industrial lager beer fermentation. Additionally, the effect of temperature on the fermentation rate was investigated. To determine if the metabolism of by-products was affected, a few higher alcohols and organic acids were monitored throughout the fermentation. Monitoring of degrading sugars and the production of ethanol with HPLC proved to be suitable. It is concluded that the fermentation rate is increased when the temperature is increased, however, further studies are needed to obtain more decisive results regarding secondary metabolite formation.