Flavours & Fragrances Food Quality Food

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.