The levels of selected volatile components that affected the sensory properties of a lager beer were optimized under high-gravity brewing conditions (15.5 °P) in an industrial plant. The influence of different pitching rates (6-10 million cells/mL), aeration levels (8-12 mg/L), times (4.5-13.5 h) of filling CCTs (cylindroconical tanks, 3850 hl), and fermentation temperatures (8.5-11.5 °C) on the contents of acetaldehyde, diacetyl, acetone, 2,3-pentanedion, dimethyl sulfide (DMS), and on the sensory properties of beer were investigated. Response surface methodology (RSM, Box-Behnken design) was used to research the possibilities for optimizing the concentration of selected volatile components and sensory properties of bottom-fermented lager beers. Statistical analyses of the results showed that the experimental factors had a significant influence (R-squared for the original model with no significant lack-of-fit) on some of the volatile components. Based on the Multiple Response Optimization analysis, the values of independent factors that ensured the highest beer sensory quality were the following: a pitching rate of 10 million cells per mL; a fermentation temperature of 11.5 °C; an aeration level of 12 mg/L; and a CCT filling time of 4.5 h. These results proved that RSM modelling can be successfully applied to optimize fermentation and lagering processes in an industrial plant to manufacture lagers of enhanced sensory quality.
Keywords: beer production; bottom fermentation; large scale; response surface methodology; volatile components.