Retail Beer & Wine Display Lighting
| "... beer in the regular amber
bottle will begin to be noticeably 'lightstruck' within about
two
minutes, while beer in a clear glass will begin deteriorating
within 30 seconds!" |
The light-struck effect is well documented in beer and light
wines.
Mercaptans (the same chemicals
skunks use as defense) are created when beer and white wines
are exposed to light (UV and visible light) for even very short
periods
of time. |
Beer and Wine References
When
Your Beer Really Stinks. Beer Break, Vol. 1, No. 16.
| "The smell is the product of the chemical reaction that takes place
in the bottle when bright light strikes the hops, creating what's
technically known as 'light struck' beer. The reaction
is stronger with paler and hoppier beers. The resulting chemical
is identical to that in a skunk's defense system, and light-struck
beer puts off one of the most powerful aromas around." |
An Introduction to the Brewing Process: Comments on Bottled Beer. R.G.
Black, revised by G.J. Kitz. Prepared for Great Western Brewing Company
Limited.
"Beer is highly susceptible to light, and we might add, light
from any source. In sunlight, the reaction is almost immediate.
The ultraviolet
part of the light spectrum breaks down the sulphur containing molecules,
forming highly odourous mercaptans and other sulphurous compounds.
A customer complaint on this subject cannot possibly be mistaken,
as a most objectionable odour and flavour is present."
"A surprising fact is that beer in the regular amber bottle will
begin to be noticeably 'lightstruck' within about two minutes,
while beer in a clear glass will begin deteriorating within 30 seconds!"
|
UNC
Chemists Figure Out What Causes 'Skunky Beer.' David Williamson. University
of North Carolina News Service, 2001.
| "Historically, beer has been stored in brown or green bottles
to protect hop-derived compounds from light in a process we call
photodegradation," said Dr. Malcolm D. Forbes, professor of
chemistry.
"Hops help flavor beer, inhibit bacterial growth and are
largely responsible for the stability of the foam in the head," Forbes
said. "Hops, however, are light-sensitive, and the three main
compounds in them identified as being light-sensitive are called
isohumulones. When attacked by either visible or ultraviolet light,
these break down to make reactive intermediates known as free radicals
that lead to the offensive taste and skunky odor."
|
Spencer's
Beer Page: Graph of Bottle Glass Light Transmission. Spencer
Thomas and Ian Craig.
"The critical part for beer skunking seems to be wavelengths shorter
than about 500nm."
"Note that the brown bottles transmit a lot less light
in this part of the spectrum than do the
green and clear bottles."
|
520
nm. Dave
Suurballe. Forum on Beer, Homebrewing, and Related Issues. Homebrew
Digest #758 Fri 08 November 1991.
"Volume 8, Number 2 of New Brewer (March-April 1991) mentions
the
magic number on page 10 in an article by Owens-Brockway entitled
' The Right Glass':
"'The degeneration problem occurs most frequently in warehouses
or
retail outlets where fluorescent lighting is the norm. While
all light with the wavelength of 520 millimicrons has the potential
to cause beer skunkiness, it is the ultra-violet (UV) portion
of
the
light spectrum below 400 millimicrons that is the most harmful
to beer in the shortest period of time. (See graph.) In fact,
it can
affect beer flavor in as little as 24 hours.'"
"The graph, which I obviously cannot reproduce, shows that amber
glass transmits about 5% of the light below 400 nm (UV), green
glass about 80%, and clear glass about 90%. Between 400 and 520
nm (green), amber glass climbs from 5% to 30%, green drops from
80% to
50% (at 450 nm, which is blue-green) and then climbs back to 80%,
and clear glass stays around 90%." |
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