Using sound waves to brew beer

Brewing beer involves a complex biological process that requires lots of resources to adequately monitor what’s going on in the fermentation tank.  To make life easier for brewers, engineers at Tzero applied their expertise in acoustics to develop a remote monitoring solution that correlates sound waves to common brew metrics and provides continuous insight into the fermentation process. 

“Fermentation—especially for beer—is complicated because it starts in one state and ends in another,” explained Eli Hughes, co-founder of Tzero Labs. “As a consequence, there is no one measurement that can tell you precisely what the yeast and beer are doing.”

As beer ferments, its density changes. In order to determine the amount of alcohol in a beer, brewers typically compare its specific gravity before and after the fermentation process. What happens in-between is more art than science.

How it works

The centerpiece of the Tzero's brewing solution is a patent-pending, sonic density sensor made of a piezoelectric ceramic that actually takes three different measurements. “As beer ferments, its density changes and so does the speed at which the sound waves travel through it. So, we measure the velocity of sound and temperature, and using those two variables we can back out the density of the fluid,” explained Hughes. Gravity measurements are temperature corrected and can be viewed as SG or °P.

Taking things one step further, Hughes pointed out that as the yeast consumes sugars in the fermentation tank, it emits CO2 bubbles that interact with the sound waves, producing another measurement that shows how much fermentation has taken place. “The acoustic scattering is directly correlated to the number of bubbles and their size and shape, so it’s a measurement that we kind of get for free because we have precision in the other two measurements,” he said.

This kind of “RPM” gauge of how quickly the yeast is eating the sugars is highly useful for brewers, who may want to take action—such as increasing the temperature or adding more yeast—if the yeast is not as active as they think it should be. “Typically yeast activity is only checked at most once a day, now brewers can get a continuous view of what’s going on in the tank,” said Hughes.

Once fermentation starts, the alcohol content, current specific gravity, fermentation activity, and temperature can be viewed from anywhere in real-time on a digital brewery dashboard.

While the fermentation process happens over days, Tzero’s brew system is generating data constantly. Hughes explained that while the sensor has quite a bit of processing capability, it is more economical to do the bulk of the data processing in the cloud.

Although the team initially started down the road of using Wi-Fi for connectivity, that didn’t prove feasible as a business model. “We were either burning up so much time helping to debug customer’s router problems or running into exactly the opposite with more tech-savvy customers that had specific demands for putting an IoT device on their network. So I planted my flag in the cellular world pretty early on,” said Hughes. “As part of the service, we pay for the cellular connection, which make sense because we can negotiate rates with the carriers.”

Another benefit for customers: The sensors are constructed from 304 Stainless Steel and can be cleaned in place, something brewers—some of whom work 60-hour work weeks—were adamant about.

As for additional applications, Hughes said that the algorithm can be tweaked for other distilled spirits and that cooling systems used in medical equipment or facilities management are another candidate, noting that the sensor can be used to monitor the mix of things like glycol and water.

He also is passionate about synthetic biology applications, for which fermentation is a workhorse.  “There is a lot of focus right now in figuring out to synthesize materials as alternatives to food resources that may be interrupted by forces such as climate change,” Hughes noted. “Or, some day we may inhabit another planet that would require the onsite production of impossible burger-type foods and we'll need fermentation tanks to do that.”

Given that, one might say that as far this sensor is concerned, the sky may not actually be the limit.

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