Abstract
Application of audible sound to microbial cultures has the potential to enhance growth and reduce fermentation time, but the reported effects vary between studies. Many studies have used air-to-liquid sound application, which may result in changes to the sound properties due to it passing through various media. This study investigates the effect that the particle motion component of audible sound has on beer fermentations using linear actuators (LAT) that predominantly deliver the particle motion component of sound rather than the pressure component. The fermentation experiment was conducted twice independently to account for possible batch variation, referred to as experiment #1 and experiment #2. Standardized wort with Saccharomyces cerevisiae Safale US-05 (~10 million cells/mL) was distributed into laminated bags (2 L) and subjected to either continuous 800–2000 Hz stimulation as the sound treatment delivered using LATs or no sound stimulation as a control treatment. Measures of wort gravity and yeast cells in suspension were used to monitor the progress of fermentation. Headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry was used to measure the abundance of volatile organic compounds (VOCs). During fermentation, the LAT treatment had a lower mean wort gravity at 24 h (p < 0.05) (experiment #1) and at 29–92 h (experiment #2) compared to the control. The LAT treatment had higher mean number of yeast cells in suspension (p < 0.05) at 24, 72, 92, 120, 144 h (experiment #1) compared to the C. Similar results were obtained for experiment #2 but at 36 and 78 h only. The fermentation ended 21–31 h earlier in the LAT treatment than the control (p < 0.05) in both experiment #1 (2.0 °P) and #2 (2.1 °P) with only subtle corresponding effects on the VOC profile. These results suggest that sound stimulation with LATs could be used to increase brewery efficiency by decreasing beer fermentation time without significantly influencing flavour.
• Audible sound was applied in beer during fermentation.
• Linear actuator increases the ratio of particle motion to pressure component of sound.
• The application of sound significantly decreased the beer fermentation time.
• Audible sound did not consistently impact abundance of volatile organic compounds.