Browsing by Author "Nikander, Vertti"

Mixed culture beer contains additional microbes in addition to brewing yeast, Saccharomyces cerevisiae. Typical microbes found in mixed culture beer are lactic acid bacteria and other yeast species than S. cerevisiae. Mixed culture beers are usually sour so they can be also called sour beers. They also contain a very small number of hops. German Berliner Weisse and Belgian Lambic are traditional mixed culture beers. Craft beer has made mixed culture beers more popular. This has led to development of new kinds of mixed culture beers. The goal of this study is to establish, can alternative souring microbe be used in brewing. This study wanted to establish does the microbe grow in beer, what kind of substances it produces and how does it affect the sensorial qualities of beer. The study was executed by making two identical beers, which the other was inoculated with the souring microbe and yeast and the other with only yeast. CFU/ml of the souring microbe and yeast was determined by plating. In addition, the most vital carbohydrates, organic acids and the ethanol content together with volatile compounds was determined by liquid and gas chromatography respectively. Samples were taken a duration of three months after which there was a sensory evaluation with a trained panel. Based on the results the souring microbe is suitable for brewing. It grew in beer during fermentation and after bottling. Based on the sensory evaluation, beer containing the souring microbe did not differ considerably compared to beer containing only yeast. It was evaluated to be very similar in measured attributes in the sensory evaluation. The biggest difference between specified substances were in organic acids only found in beer containing the souring microbe. Also, beer containing the souring microbe had deviation in maltose and ethanol content possibly because of contamination. Differences between volatile compounds were small in the two beers respectively. More study is needed to optimise the fermentation process and improve the sensorial qualities with more sensorial study.