Managing Dissolved Oxygen Levels | Brewing Industry Guide
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Managing Dissolved Oxygen Levels

Here are a few simple ways to troubleshoot oxygen in your process and in your packaging workflow to ensure that you serve beer that tastes the way you intend it to.

Alexis Foreman October 03, 2018

Oxygen is both a brewer’s friend and foe, giving yeast what it needs to breathe and thrive through the fermentation process but then becoming Enemy #1 of bright and expressive flavors after the yeast has done its job.

Every process or transfer a beer is subjected to post-fermentation is an opportunity for oxygen to find its way into your beer and begin that process of staling, muting, and reducing shelf life, and the packaging process is one step that presents particular risk. The added oxygen that results from putting beer into cans, kegs, or bottles can impact the quality and taste of the final product.

As a brewer, you tend to focus on making the best-tasting recipes, and packaging is sometimes an afterthought. Having insight into how the brewing process and packaging will ultimately affect the flavor of your beer can give you the confidence you need to create award-winning flavors that consumers will love, no matter how long the beer sits on the shelf.

DO Basics

First, the basics. Dissolved oxygen (DO) is the amount of oxygen that is incorporated into the liquid during the brewing process. All beer has dissolved oxygen, but when and how you handle the beer during and after the fermentation process affects the quantity of DO in the beer. Managing the amount of oxygen is an important step in the beer-making process but grows exponentially more important the longer your beer’s life span. If you sell everything you brew within a week over your taproom bar, it may not be as crucial to minimize DO throughout your production process. But if you package beer in any form, you should understand where and when oxygen is introduced so you can ultimately minimize oxygen pickup from fermentation through packaging and allow customers to experience your beer the way you intend it.

Measuring DO

Testing for DO can be a daunting task, and when in the process you test is important. To accurately measure for DO, it’s important to maintain a consistent methodology with a focus on results and trends. Once fermentation is complete, there are few ways to reduce DO in your beer but many ways to add it, so the first place to measure DO in your process is after primary fermentation, before dry hopping.

Keep a log of DO levels. Measure again after dry hopping to see how that process added DO to the tank. When you transfer to a bright or packaging tank, test DO again. If the DO level has increased significantly, do some research to determine whether the tank was properly purged or whether there was any oxygen pickup through the pump or any of the hose gaskets. Track and log methodically to identify any phantom sources of oxygen in your beer.

When you package, check DO levels in the tank again and once more at the filler to make sure your pump and hoses are not adding DO to the beer. Keep a running log and test fills throughout the day, measuring temperature, carbonation level, and tank pressure to help ensure consistency from batch to batch. It is best to measure when the beer comes directly off the line with an instrument that is calibrated to a known standard to ensure the most consistent results.

DO in Packaging

Some packaging systems create unrealistic expectations about DO pickup with claims such as “Our system picks up xx ppb” or “x–y pickup possible” that are often inaccurate and misleading. DO pickup is nonlinear and can be affected by temperature, pressure, the amount of oxygen in the beer before packaging, and a variety of other factors. But since we know that packaging presents particular risk of DO pickup, testing temperature, carbonation, and pressure can help identify potential areas to troubleshoot.

You should take measurements from several places, including the tank, the beer manifold before the fill heads, and both shaken and unshaken cans. Having all those points of reference can help you determine exactly where the DO is being introduced into the beer and, more importantly, shine light on problems as they arise so they can be addressed.

Here are some things to look out for to maintain low levels of DO in packaged beer.

  • Incoming DO. As I’ve said above, it’s important to know the DO number in the bright tank. The lower this value, the better. The more DO in the beer before packaging, the more DO in the beer overall.

  • Leaks. Pinhole leaks or residual air in the hoses coming out of the bright tank can add oxygen to the beer. Gland retainers, O-rings, butterfly valves, and tri-clamp gaskets can leak and cause DO pickup. If beer is leaking out, oxygen is coming in.

  • Temperature. Ideally, beer should be kept cold enough to pour well and still generate foam (34°F/1°C).

  • Rinsing/sanitizing the package. Oxygenated sanitizer or even residual rinse water that has not been de-gassed could increase DO.

  • CO2. Control over the pre-CO2 purge, especially in open-fill systems, is essential. CO2 is heavier than air, so gently filling the package from the bottom and stopping before the top in a pressure-controlled environment is key.

  • Exposure to air. When beer is exposed to air between cycles, it can pick up DO; therefore, control over the time from fill to closure is important. Even changes to outside air from air conditioners, heaters, or open windows can increase the risk of picking up DO. Residual product on fill heads and foam scrapers is exposed to air between cycles. When beer remains on the filler as it is retracted, it can pick up extra oxygen and re-introduce it into the next can or bottle.

  • Foam. A foam cap is by far the most important factor for reducing DO. Fill speed, foam, and fill volume are the biggest contributors to unwanted DO in packaging. Filling quickly with no foam makes the machine run faster, but DO numbers can be higher as well. Ideally, control over all aspects of the fill cycle will enable the operator to generate a proper foam cap. Some manage that risk with underlid gassing, but it’s not a cure-all. It can help keep DO at a minimum, but pressures that are too high will eliminate foam and introduce air through turbulence, and pressures that are too low won’t achieve reduced oxygen levels.

  • Seaming/capping. Time to closure and control to closure are also important. It’s crucial to make sure that the final capping or seaming happens as quickly as possible with little agitation to the product to keep oxygen from being introduced into the beer.

Packaging systems, similar to beer recipes themselves, need to be learned, adjusted, and optimized over time to get the optimum results. The good news is that today’s packaging systems can help minimize the amount of DO added in the packaging process, as the topic is front of mind for every system manufacturer and is often the first question every brewer asks.

No matter how you package (cans, bottles, crowlers, growlers), with best practices, high-quality monitoring equipment, consistent measuring methods, and troubleshooting, packaging beer correctly can reduce the amount of DO and preserve the integrity of your beer. It’s important to factor in DO levels throughout the entire life cycle of the product.

How beer is made, packaged, and delivered can affect the flavor and quality of the final product. But with the right training, experienced operators, a good packaging system, and trial and error, you can manage DO levels and focus on what you do best—making great-tasting beer.

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