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.