This method is suitable for the determination of steam-volatile aroma compounds in wort.
Volatile aroma compounds are driven out of the sample through steam distillation. The ethanol distillate is adjusted to be alkaline and saturated with NaCl. The extraction of the aroma compounds is performed by shaking out with dichloromethane and the phases separated by centrifuging. The organic phase is further concentrated in a stream of nitrogen gas. An ammonia solution is added to remove the acids, because the acids would co-elute, thus preventing quantification of the target substances.
Determination of total diacetyl in beer.
The method is suitable for beers of all original wort ranges and alcohol contents.
Beer is thermally treated to cause the precursors present in the sample to transform into their respective vicinal diketones. Using the headspace technique, the concentration of total diacetyl is determined using gas chromatography. The linearity of the detector and the determination of the concentrations of analytes in the sample are achieved by using multiple concentration levels within their relevant range and through evaluation of the relative area under the peaks. Depending upon the operating conditions of the chromatograph, the relative areas under the peaks can also be used to determine the concentrations. The method is suitable for beer brewed to any original gravity or to any alcohol content.