Productivity of immobilized yeast reactors with very high gravity worts

In the competitive world of beer production, efficient utilization of raw materials and equipment together with smooth operation are advantageous. In this study, data from laboratory-scale main fermentations with original gravities between 15 and 24°P and immobilized yeast are presented. The worts were prepared from malt extract, and lower original gravities were obtained by diluting the 24°P wort with brewery water. The yeast strain used was a production strain from a brewery. Porous glass beads were used as the carrier. The optimal gravity found in regard to ethanol productivity was between 18 and 21°P. The highest ethanol concentration in the beers was over 10% (v/v). The aroma compound profiles of the beers produced were quite similar, except for acetaldehyde. The laboratory-scale fermentations using immobilized yeast may be an effective tool to screen for ethanol-tolerant strains or to find process parameters that facilitate very-high-gravity brewing.