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VIEW ARTICLE DOI: 10.1094/ASBCJ-54-0191
Detection and Identification of Oils in Beer by FTIR. Karen E. Skinner, Brewing Technical Services, Anheuser-Busch Inc., One Busch Place, St. Louis, MO 63118; 314/577-2850; Fax 314/577-1055. J. Am. Soc. Brew. Chem. 54(4):191-197. Accepted April 12, 1996.
Oils were extracted
from finished
beers by filtration
through polytetrafluoroethylene
(PTFE) (Teflon)
membrane filter
pads and from
in-process beers
by stirring
with diatomaceous
earth. The oils
were then eluted
from the filter
pad or diatomaceous
earth with 1,1,2-trichlorotrifluoroethane
(Freon 113).
The eluant was
concentrated
to a known volume
and analyzed
by measuring
the Fourier
transform infrared
(FTIR) absorbance
of the oil peaks
at 2930 cm(^-1)
in a fixed pathlength
cell. The concentration
of oil present
was determined
by comparison
with a standard
curve. Standards
were prepared
by dissolving
various oils
and lubricants
in 1,1,2-trichlorotrifluoroethane.
Low concentrations
of oils, up
to 0.2 mg/L,
were found in
virtually all
normal canned
beers. The oil
found in these
beers had as
its probable
source the petrolatum
used as a lid
stock lubricant.
Tetrachloroethylene
was investigated
as an alternative
solvent to 1,1,2-trichlorotrifluoroethane.
The extracted
oils were qualitatively
identified by
concentration
of the extracts
to a few drops,
which were then
applied to a
potassium bromide
salt plate.
After evaporation
of residual
solvent, the
infrared spectrum
of the cast
film of the
extracted oil
was recorded.
Keywords: Beer,
FTIR, Infrared,
Lubricant, Oil.
Aceites
fueron extraídos
de cerveza terminada,
pasando ésta
a través
de filtros de
membrana PTFE
(teflón),
y de cerveza
en proceso por
agitación
con tierra de
diatomeas con
1, 1, 2-triclorotrifluoroetano
(Freon 113).
El eluente fue
concentrado
hasta un volumen
conocido y analizado
midiendo la
absorbancia
en el infrarrojo
(FTIR) de los
picos de los
aceites a 2930
cm(^-1) en una
celda de longitud
fija. La concentración
de aceite presente
se determinó
por comparación
con una curva
estándar.
Estándares
fueron preparados
disolviendo
varios aceites
y lubricantes
en Freon 113.
Tetracloroetileno
fue investigado
como otra opción
al Freon 113.
Los aceites
extraídos
fueron identificados
cualitativamente
al concentrar
los extractos
hasta unas cuantas
gotas y aplicando
éstas
a placas de
bromuro de potasio.
Después
de evaporarse
el solvente
residual, se
obtuvo el espectro
infrarrojo de
la capa de aceite
en la placa.
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A subscription to the Journal of the American Society of Brewing Chemists is complimentary with membership to the ASBC. The ASBC Journal publishes scientific papers, review articles, and technical reports dealing with the chemistry and microbiology of brewing ingredients and relevant technology, as well as the analytical techniques used in the malting and brewing industry. |