06/23/2020 | Brewing | 9 MINUTE READ

Testing Dissolved Oxygen in Beer for Commercial Breweries

beer being poured into glass cup

An important component of managing a commercial brewery is maintaining the right amount of dissolved oxygen for fermentation. Dissolved oxygen is the amount of oxygen that has been dissolved in the water. While fish and other organisms require dissolved oxygen to survive, measuring this kind of oxygen in the water is also important for a wide range of additional processes, one of which is the brewing of beer. It’s relatively easy to measure dissolved oxygen, which can primarily be done with galvanic dissolved oxygen sensors and optical dissolved oxygen sensors.

There are many reasons why it’s important to monitor dissolved oxygen, which extend from making sure that a wastewater treatment facility is working as intended to properly brewing beer to a finished product that customers will enjoy. When manufacturing beer, dissolved oxygen is important for two critical components of the beer-brewing process.

This article goes into detail about why it’s important that your commercial brewery tests the amount of dissolved oxygen in beer.

Beer and Dissolved Oxygen Basics

guinness symbol beer factory building

Dissolved oxygen simply refers to the amount of oxygen that has dissolved in water. Keep in mind that this oxygen is different from the oxygen that exists in water molecules. When running a wastewater treatment facility, dissolved oxygen levels can indicate how effective the plant has been at dissolving waste. Dissolved oxygen is a very important component of the beer-making process that’s integral to two core aspects of this process.

In order to understand the importance of dissolved oxygen when brewing beer, it’s important to look at the ingredients that are used when making beer, which include yeast, water, hops, and cereal grains. Dissolved oxygen is important for the fermentation process that occurs when making beer, which is necessary to give the beer its carbonation and alcohol content. Along with fermentation, having the right DO levels at the beginning of the brewing process will dictate how well the beer is made.

Beer-brewing Process

golden barley in wild

The beer-brewing process begins with selecting the right type of cereal grains, which could be anything from barley and wheat to oat and rice. In order for these grains to actually germinate, air is sent onto the grains while they are kept in storage, which creates an environment that’s rich in oxygen. Once this process is completed, the grains are completely malted. The grains are then mashed up before being mixed with water in order to create wort. The wort is boiled for upwards of 30 minutes to kill any bacteria that remains.

It’s at this point that yeast is mixed in with the wort. In order for the fermentation process to occur, yeast needs to be added to the mixture. The exact amount of yeast that’s added to the wort depends on the temperature of fermentation, the strain of yeast, and the wort gravity. When the fermentation process occurs, the glucose that’s found in the wort will break down to form alcohol and carbon dioxide. If you want the fermentation process to be successful in your commercial brewery, it’s essential that the dissolved oxygen is at the right levels throughout this process.

Once fermentation has taken place, hops are added to the beer to enhance the flavor profile, aroma, and bitterness of the substance. There are many different types of hops that a commercial brewery can use when making beer, each of which can create a different taste. After the hops have been added, water will be combined with the mixture to dilute the alcohol content.

The quality of the water in question can determine how the beer tastes. The best commercial breweries can typically be found in locations where clean water is in abundance. Keep in mind that water quality can be measured with pH sensors. While the four ingredients mentioned previously are all necessary if you want to brew a delicious beer, this process can’t be successful if dissolved oxygen levels aren’t correctly maintained.

Maintaining Optimal Levels of Dissolved Oxygen in Beer

men looking at cups of beer in factory

While it might seem difficult to maintain optimal levels of dissolved oxygen when making beer, the process of doing so is fairly simple. It’s also easy to measure DO levels, which should allow you to quickly identify readings and make the necessary alterations without a delay in the brewing process. In most cases, dissolved oxygen is added once the wort has been boiled but before yeast has been added to the solution. For the fermentation process to be successful, dissolved oxygen levels should come in at around 8-12 PPM. It’s believed that five PPM is the lowest the readings can be in order for the yeast to grow correctly. However, you also shouldn’t go past 17 PPM.

The majority of commercial breweries will oxygenate the wort with sterile air once it has cooled down. While there are some breweries that choose to oxygenate the wort when it’s still boiling, doing so can create issues with the flavor profile that results in a garlicky taste. No matter when you choose to add the oxygen to the wort, it’s important that you complete this process before fermentation has begun. Oxygen is used less and less as the fermentation process goes on, which means that adding oxygen later on in the process will result in some dissolved oxygen being left over with the finished product. Too much dissolved oxygen in your final product can make the beer taste stale.

As touched upon previously, it’s important that you maintain DO levels of 8-10 PPM, which should result in a beer that has been properly fermented. When conducting high-gravity brewing, your DO levels should be closer to 15-17 PPM. If you don’t place enough DO in the wort, your commercial brewery will likely experience a low and relatively sticky fermentation, flavors that don’t taste right, and a low alcohol production. With high DO levels, too much yeast will grow, which worsens beer production. The beer will also taste somewhat fruity because of the high amount of ester that’s produced. To maintain DO levels, make sure that you pair your aeration system with a quality DO sensor.

Factors that Affect Dissolved Oxygen Levels

beer being preserved in foam cap in cup

There are several different factors that can affect dissolved oxygen levels, all of which you should be aware of to make sure that the finished product has the right taste. For one, it’s essential that you understand how much dissolved oxygen is located in the bright tank. Lower DO values will result in a better beer once it’s been packaged. Keep in mind that the bright tank is necessary to hold the beer until it’s ready to be packaged. There’s also a possibility that the hoses connected to the bright tank could leak, which would lead to beer leaking out and oxygen coming in. To protect against this issue, manually inspect the bright tanks on a regular basis.

The surrounding temperature can affect dissolved oxygen levels as well. Beer should typically be kept in temperatures around 34 degrees Fahrenheit, which will help you maintain DO levels while also making sure that the beer generates enough foam when poured. During the entire brewing process, it’s important that the beer isn’t exposed to too much air. Open windows and air conditioners can affect how much DO gets into the product.

Likely the best way to maintain DO levels is by implementing a foam cap. Fill speed, fill volume, and foam can cause high amounts of dissolved oxygen to get into the beer before it has been packed. If you’re steady and consistent with how you package the beer and fill the bottles/cans, you should be able to minimize the amount of DO that gets into the finished product.

When Do I Test Dissolved Oxygen for Breweries?

factory brewery beer giant containers

While oxygen should be added to beer after the wort has been boiled and before the yeast has been added to the solution, it’s important that you wait to test for DO until later on in the process. When the beer has been properly fermented, it’s very difficult to reduce the amount of dissolved oxygen but easy to add DO, which is why it’s recommended that you test for dissolved oxygen levels after fermentation but before the hops have been added. After you obtain measurements, the readings should be placed into a log book for future reference.

Once the hops have been added, you should measure DO levels again to identify how much DO was added during this process. Make sure to test again when the beer has been transferred to the bright tank before packaging. If the DO amounts have increased substantially, check to make sure that no DO pickup occurred from the hoses on the bright tank. Log every measurement you obtain throughout this process. DO should continue to be checked after the beer has been packaged at the tank and the filler.

Along with testing dissolved oxygen, it’s also important that you maintain tank pressure, temperature, and carbonation level if you want consistent results with your packaged beer. If you don’t regularly test dissolved oxygen levels, you run the risk of the dissolved oxygen becoming too high or too low, both of which are issues that could lead to poor-tasting beer. Regularly testing DO levels will help you identify what step of the process may be causing high amounts of oxygen to be added to the beer, which should allow you to correct these issues early on.

Measuring Dissolved Oxygen in Beer

There are three basic types of dissolved oxygen sensors that you can use to measure the amount of DO in your beer, which include:

  1. Galvanic DO sensors
  2. Polarographic DO sensors
  3. Optical DO sensors

All of these sensors are effective at measuring dissolved oxygen and can be readily installed in nearly every aspect of the beer line, which include around the valves and bends. However, you should never place one of these sensors in pumps or at CO2 injection sites.

The measurements that you receive will be provided as PPM readings. To make sure that you’re provided with accurate readings, the sensor should be installed horizontally. Vertical installations can lead to the development of an air pocket. As long as you measure DO levels regularly and keep logs of every reading, you should be able to properly maintain DO levels.

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Posted by Sensorex on June 23, 2020

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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