Is Drinking Oxidized Beer Safe?

Oxidation is a process that is generally considered ruinous to beer. It occurs when beer is exposed to oxygen during the brewing process, from the brewhouse to the fermentation cellar, to the packaging line, or even within the bottle in storage after packaging. While it is unsafe to drink oxidized beer, oxidation itself does not make a beer unsafe. Rather, it affects the beer's taste and appearance, giving it stale notes that can be described as leathery, papery, or wet cardboard-like.

Oxidized beer is safe to drink, but it's a matter of taste

Oxidation is generally considered ruinous to beer. Beers that have undergone oxidation are often described as having stale, cardboard-like, catty, or blackcurrant notes. However, while oxidized beer is typically undesirable, it is not unsafe to consume. The decision to drink oxidized beer ultimately comes down to a matter of taste.

Oxygen exposure can occur anywhere in the brewing process, from the brewhouse to the fermentation cellar, the packaging line, or even within the bottle during storage. The more oxygen a beer comes into contact with, the faster and more severe the oxidation. Cooler storage temperatures can slow down the process. The Beer Judge Certification Program (BJCP) describes oxidized beer as exhibiting "any one or a combination of stale, winy/vinous, cardboard, papery, or sherry-like aromas and flavors."

While oxidation typically imparts negative flavours to beer, in certain styles of beer, and under controlled conditions, oxidation can actually improve the beer. For example, during the long vat storage and barrel ageing of lambics prior to bottling, or during the gentle bottle ageing of barley wines, slow and graceful oxidation can add complex flavours, make the brew more robust, and increase its longevity. Additionally, high-alcohol, dark-coloured, malt-focused beers such as barley wines, old ales, and imperial stouts can develop characteristic sherry-like flavours from oxidation that complement the dark malts.

In summary, while oxidation is generally detrimental to beer, there are exceptions where it can enhance certain styles. Ultimately, the decision to drink oxidized beer comes down to personal preference. If the beer tastes and smells okay, and meets certain safety criteria, it is safe to consume. However, it is important to note that oxidation causes beer to go bad quicker, so it is recommended to drink it soon after oxidation occurs.

Oxidation occurs when beer is exposed to oxygen

Oxygen can react with many compounds in beer, and the effects are usually negative. The most notable flavour-active compounds affected by oxidation are trace elements of fatty acids (lipids), which can make the beer taste stale and give it a pronounced flavour of wet cardboard. Oxygen can also react with melanoidins, which are created during the malting process and the kettle boil. Oxidized melanoidins can give the beer a slight taste of sherry. In cold brew, oxygen can turn alcohol into almond-tasting aldehydes.

The Beer Judge Certification Program (BJCP) describes oxidized beer as demonstrating "any one or a combination of stale, winy/vinous, cardboard, papery, or sherry-like aromas and flavours." Oxidation can also cause the beer to become cloudy and acquire a cardboard taste. However, oxidation does not always ruin beers, and some people may even enjoy the flavours that oxidation can bring. Honey and graham cracker flavours are off-flavours that can be the result of oxidation, and these may be considered positive by some drinkers.

In most cases, drinking oxidized beer is not an experience that people seek out. However, some beer styles can improve with long-term oxygen exposure, such as barleywines, old ales, and imperial stouts. These beers are generally high in alcohol, dark in colour, and malt-focused. The slow oxidation of these beers can add complex flavours, make the brew robust, and allow it to be kept for years.

Oxygen degrades the alcohols and aromatics in beer

Oxygen is a beer's worst enemy. It wreaks havoc on the alcohols and aromatics in beer, turning them into bland shells of their former selves. This process is called oxidation, and it happens when molecular oxygen comes into contact with alcohol. In beer, ethanol becomes acetaldehyde, an off-flavour compound described as tasting like green apples, latex paint, or even cut grass.

Oxygen doesn't stop there. It can further oxidise an aldehyde to an acid. In the case of acetaldehyde, it becomes acetic acid, or vinegar—perfect for a light salad dressing, but not so wonderful in a lager. Oxygen also attacks the hop compounds that give many beers their delicious bitter flavour, turning them into fatty acids. These fatty acids can be further oxidised, imparting soapy and fatty flavours to the beer.

The most common off-flavour that results from oxidation is trans-2-nonenal (T-2-N), with a flavour reminiscent of wet cardboard or old newspapers. This off-flavour is difficult to overcome, as T-2-N precursors are produced during the fermentation process of certain malts, and are not problematic until short-chain aldehydes condense with the precursors in oxidative conditions.

Brewers must be vigilant to prevent oxygen from coming into contact with beer at any stage, from brewing to bottling or kegging. Even a tiny amount of oxygen can cause significant off-flavours. To combat this, brewers use techniques such as purging tanks and bottles with carbon dioxide, employing oxygen-impermeable packaging materials, and minimising headspace in containers to reduce the contact between beer and oxygen.

While oxidation is generally undesirable, there are a few beer styles that can—but not always—improve with some long-term oxygen exposure. These are generally high-alcohol, dark, and malt-focused beers, such as barley wines, old ales, and imperial stouts. The melanoidins in these dark beers can oxidise into the characteristic flavours of sherry, complementing the dark malts. However, this is not a reason to introduce oxygen to your beer intentionally, as even these styles can be negatively impacted by oxidation.

Beer with higher alcohol content can improve with long-term oxygen exposure

Oxygen is a double-edged sword when it comes to beer. While it is essential for yeast health during the fermentation process, it can also be detrimental to the final product, causing staling, muting, and reducing shelf life. However, beer with higher alcohol content, such as barley wines, old ales, and imperial stouts, can develop and improve with long-term oxygen exposure.

The Beer Judge Certification Program (BJCP) describes oxidized beer as exhibiting "stale, winy/vinous, cardboard, papery, or sherry-like aromas and flavors." While these characteristics may not be desirable in most beer styles, they can complement dark malts in high-alcohol, dark-colored, malt-focused beers. The oxidation of melanoidins in dark beers can result in the characteristic flavors of sherry, adding complexity to the beer.

It is important to note that the presence of oxygen during the brewing and packaging processes can significantly impact the quality and taste of the beer. Brewers must carefully manage dissolved oxygen (DO) levels to ensure the desired flavor profile. DO is the amount of oxygen incorporated into the liquid during brewing, and its handling during and after fermentation affects the quantity in the final product.

Minimizing DO is crucial for beers with longer life spans, especially those packaged in cans, kegs, or bottles. The transfer of beer between vessels and the packaging process can introduce oxygen, accelerating staling and muting flavors. To prevent this, brewers should aim to minimize splashing, avoid bulk movements, and "rack quietly."

In summary, while oxygen is generally considered an enemy of bright and expressive beer flavors, specific beer styles with higher alcohol content can develop and improve with long-term oxygen exposure, resulting in unique and complex characteristics.

Oxidation can occur anywhere in the brewing process

A second major oxygen pickup location is the filling line. The amount of oxygen pickup depends on the sophistication of the bottling and kegging equipment and the skill of the operators, but achieving zero oxygen pickup is virtually impossible. The more oxygen in the packaged beer, the faster it will become stale.

Oxygen can also be introduced when transferring beer from one vessel to another (primary to secondary, fermentor to bottle or keg, etc.). The key is to minimise splashing, and avoid pouring, dumping, or other bulk movement. The same is true for homebrewers, who are at particular risk of oxidation when racking from one carboy to another or into their final vessel of choice.

The oxidation of beer is generally considered ruinous, causing stale, off-flavours. However, on rare occasions, oxidation can improve certain beers, when deliberately employed under controlled conditions. For example, during the long vat storage and barrel aging of lambics prior to bottling, or during gentle bottle aging of barley wines. Such slow and graceful oxidation adds complex flavours, makes the brew robust, and allows it to be kept for years.

Frequently asked questions