Flavor stability in Beer

EPR industrial applications

Oxidative staling of beer occurs due to a free radical process. During storage, even trace amounts of metals such as iron or copper will convert molecular oxygen to what are known as ROS (Reactive Oxygen Species).

ROS react with beer components to produce beer-derived free radicals that are intermediates in the staling process. Eventually the free radical reactions terminate with the formation of carbonyl products such as aldehydes and ketones.

: EPR intensity is recorded at several time points

It is these carbonyl compounds that give rise to the “cardboard like” flavor of stale beer. Antioxidants in beer help it to resist free radical oxidation. Oxidation is minimized in the brewery by optimizing the processing and storage conditions to provide maximum antioxidant content in the packaged beer.

Breweries use EPR spin trapping and “forced aging” to measure free radicals as they form in beer. This EPR forced aging method has been further developed in the brewing industry to provide quality control and shelf life prediction.

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