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17 Jun 2002
Ultraviolet laser light helps US and Belgian researchers clarify the photodegradation of beer.
Researchers at Ghent University, Belgium and the US University of Carolina have used ultraviolet laser light to study the photodegradation of beer.
Denis De Keukeleire and colleagues claim to be the first to use laser flash photolysis with spectroscopy to identify the free radicals that cause the bitter beer taste known as lightstruck flavor.
"Exposing beer to light causes an offensive taste and a 'skunky' odor called the 'lightstruck flavor'," De Keukeleire told Optics.Org. "Never before has this problem been investigated using dynamic techniques on a microsecond scale."
De Keukeleire and colleagues first irradiated iso-alpha-acids, the chemicals in beer that form free radicals when exposed to light, with pulsed 308 nm light from an excimer laser. Once they had triggered photodegradation, the researchers studied the reaction with a spectroscopy technique called time-resolved electron paramagnetic resonance (TREPR).
According to De Keukeleire, compared to past results the TREPR signals reveal a more detailed picture of how free radicals are produced when UV light strikes the iso-alpha-acids.
"Our work has identified the intermediates and radicals that form on illumination of the iso-alpha-acids," said De Keukeleire. "This breakthrough has let us establish the exact mechanism of photodegradation of iso-alpha-acids which are key to skunky beer."
Currently filing a patent that highlights the approach, the researchers believe that the brewing industry will profit from their innovation.
"[The industry] aim is to brew beers using raw hops while avoiding light-induced off-flavor," added De Keukeleire. "And [eventually] beers could be safely stored in clear glass or plastic bottles."
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