Application of ultrasound for enhancing fermentation rates in brewing technology.

Background: There is much promise in technologies which may speed up time-consuming processes such as preparing seed yeast, primary fermentation and improving beer quality in the brewing industry. This study focuses on the activating and disintegrative effect of ultrasound with a 44 kHz frequency and a 1.0 W/cm2 intensity on brewer's yeast.

Methods: This study established that ten-minute ultrasonic treatment of yeast is sufficient to reach the stimulating effect. Further ultrasonic treatment is irrelevant since the percentage of dead cells in the yeast suspension exceeds the permissible levels (more than 10%). The experiment showed that two-minute ultrasonic treatment improved the physiological activity of seed yeast and shortened the time for producing seed yeast by 12 hours. Ultrasonic disintegration allowed a yeast extract to be obtained from the brewer's spent yeast. Ultrasound was applied to the yeast suspension for 19 minutes.

Results: The obtained yeast extract was used for additional nutrition in preparing seed yeast. It was found that the added yeast extract (2% of the total volume) shortened the time for preparing seed yeast by 6 hours due to the improved physiological state of the yeast. At the final stage, two-minute ultrasonic treatment and yeast extract (2% of the total volume) were used to activate the seed yeast.

Conclusions: The seed yeast activation shortened the time for preparing seed yeast by 18 hours, and for the primary fermentation by 24 hours, while also improving the quality of the beer.