Determination of the percentage of nitrogen that has dissolved in the wort during the Congress mash method
Suitable for (Congress) mash
The Kolbach index is used to express the quantity of the nitrogenous substances found in malt, which go into solution under the conditions present during the Congress mash method. It is a measure of the degree of proteolytic modification of the malt and also provides an indication for the quantity of proteolytic enzymes contained in the malt. The Kolbach index is less conclusive than other methods due to its dependence on the total nitrogen content and the provenance of the barley. Therefore, it must always be considered together with the total nitrogen content.
Barley malt intended for use in beer brewing or elsewhere in the food industry
High-molecular weight dextrins and starch present in the wort extracted from brewery spent grains are precipitated through the addition of ethanol, centrifuged and dissolved in phosphate buffer, followed by the addition of an iodine solution. Depending upon the molecular weight and degree of branching, a red to blue color forms, the intensity of which is measured spectrophotometrically at 578 nm.
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.
The method is suitable for the determination of water vapor volatile aroma compounds in beer.
Volatile aroma compounds are driven out of the sample through steam distillation. The ethanolic distillate is saturated with NaCl. Potassium hydrogen sulfite is added to separate carbonyl groups that might interfere with the analysis. The extraction of the aroma compounds is performed by shaking out with dichloromethane and the phases separated by centrifuging.
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
The volatile constituents in hops or hop products are obtained by means of steam distillation. The hydrocarbon and oxygen fractions are separated using a process involving column chromatography.
Applicable for all (laboratory) wort
The Congress wort is heated in order to inactivate the amylolytic enzymes, and afterwards added to an Erlenmeyer flask along with 7.5 g/100 ml yeast where it is allowed to completely ferment out under constant agitation. The difference in the extract before and after fermentation is measured in order to calculate the limit of attenuation.