Subject: Skunked beer in cans
Date: 1992-02-29 17:38:35 GMT
I am familiar with the phenomenon of light-struck beer in bottles,
where UV radiation breaks an isohumulone bond, creating a ketyl-acyl radical
pair. Loss of CO by the acyl radical forms the 3-methyl-2-butyl radical,
which then combines with a thiol radical from sulphur- containing proteins
to produce 3-methyl-2-butene-1-thiol.
In college, we learned the hard way that when a previously cold can
or bottle of beer is warmed up (say, in the trunk of a car), and then cooled
down again, the beer develops an off-flavor which is similar to, if not
identical to light-struck beer. Does anyone know if the temperature changes
in the absence if light can lead to the same chemical changes that produce
light-struck beer? Or is this phenomenon perhaps related to "freezer-burn"
that happens to other foods?
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