Impact of Successive Exploitation of a Saccharomyces pastorianus Starter Culture on Saccharide Uptake Dynamics from Wort

Abstract

Research background. The production of lager beer includes successive repitchings of a single Saccharomyces pastorianus starter culture. During the beer production process, the yeast is exposed to several stress factors which could affect the fermentation performance. An incomplete fermentation represents a waste of fermentable extract and leads to a beer with higher carbohydrate levels, which could result in a beer with an atypical flavour profile. The aim of the present study was to determine the impact of successive exploitation of a single starter of an S. pastorianus culture on the wort saccharide uptake dynamics. Experimental approach. The fermentation process was monitored during the production of twelve batches of beer, where the starter yeast culture was reused twelve times without any further treatment. The following beer production steps were monitored: wort production, yeast starter culture propagation, primary fermentation, secondary fermentation and the final product. The work was conducted on an industrial scale employing standard process conditions. Results and conclusions. Monitoring of the starter culture viability during successive fermentations indicated no reduction in the viability and vitality of the yeast culture. Monitoring of the fermentable wort saccharide concentrations (glucose, fructose, disaccharides and trisaccharides) revealed a correlation between an improvement in saccharide utilisation and starter culture age. Saccharide uptake efficacy proportionally matched the repitching frequency. Successive exploitation of a S. pastorianus starter culture has a positive impact on the dynamics of saccharide utilisation from classical hopped wort and the young beer. However, the final lager beer contains no residues of fermentable saccharides that could affect the overall quality and flavour profile. Novelty and scientific contribution. Results showed the impact of twelve successive wort fermentations on the dynamics of saccharides uptake that gives brewers important information. The added value of the experiment was all the work that was done at the industrial scale, with control of all processes and usage of exactly the same raw materials. This study contains usable technological data on behaviour of saccharides during brewing process in real industrial scale, which is not yet to be found in the literature.