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Lightstruck Or ‘Skunky’ Beer
Lightstruck, or skunked beer as it is commonly known, is a beer with off-aromas and a tainted flavour. Certain compounds in hops, the main preserving agent in beers, are light sensitive and when they are exposed to strong sunlight a photo-oxidation reaction takes place. It creates an intense flavour compound that is abbreviated to ‘MBT’. This pungent aroma is often compared to that of a defensive skunk due to the potency and characteristics. Hence the name. It can be recognised as having a sulphur smell/taste.
In strong sunlight this reaction can take place almost instantaneously. Whilst it is a chemical reaction and ultimately unpleasant in the beer, it is worth noting that it is in fact safe to drink and will not make you ill.
In order to prevent this from happening, it is advised that you do not leave your brew fermenting in direct sunlight. Whilst many of the fermenters are of an opaque nature, they do not prevent all the sunlight getting to your beer. Furthermore, clear and green bottles are not really effective in cutting out the harmful ultraviolet (UV) rays from your prized liquid. The best colour to use is brown bottles. This works as a filter. We would also recommend that if you are storing the beer it be done in somewhere shaded or dark.
Unfortunately if your beer has become lightstuck or skunked, you have passed the point of no return! The chemical reaction has already taken place and cannot be reversed. Not in a domestic environment anyway.
Chris Marshall – brewathome.shop (Last Updated: 16th October, 2022)