Determination of the concentration of quaternary ammonium compounds (QAV) in disinfectants.
Suitable for all solutions containing quaternary ammonium compounds (QAV).
Many basic dyes (e.g. methylene blue) behave in a similar way to cation-active substances. Methylene blue forms a complex with dodecyl sulfate (anion-active surfactant), for example, which is soluble in organic solvents such as dichloromethane with blue colour. By adding quaternary ammonium compounds (QAV), this complex is decomposed and the methylene blue migrates from the dichloromethane into the aqueous phase. When titrating quaternary ammonium compounds with dodecyl sulfate, this process takes place in the opposite direction, i.e. the methylene blue migrates from the aqueous to the dichloromethane phase. The end point of the titration is reached when the aqueous and dichloromethane phases have the same colour depth.
Or to put it in other words:
Methylene blue (water-soluble dye in cationic form) forms a complex with dodecyl sulfate (anionic surfactant), which is soluble in organic solvents, e.g. dichloromethane, with blue colour. On the other hand, QAV also forms a complex with dodecyl sulfate, so that the indicator migrates into the organic phase once the equivalence point has been exceeded.
Valid for all non-turbid beers
By incrementally adding increasing amounts of a saturated ammonium sulfate solution to beer, haze appears as a result of protein precipitation. The amount of the ammonium sulfate solution necessary to produce haze is directly proportional to the stability of the beer. The ammonium sulfate precipitation value expresses the ml of saturated ammonium sulfate solution that must be added to 100 ml of beer in order to produce a barely perceptible opalescence.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
Ammonium ions react at a pH of approx. 12.6 with hypochlorite ions and salicylate ions in the presence of sodium nitroprusside, which serves to catalyze the reaction, to form a green color (indophenol blue).
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
In an acidic solution, in the presence of ammonium molybdate, dissolved silicic acid or silicates produce silicomolybdic acid which exhibits a yellow color. After the addition of a reducing agent, a blue color emerges which is proportional to the quantity of the silicic acid present in a certain concentration range.
A defined amount of formaldehyde is added to beer. Haze forms in the beer which is correlated with "warm days".
Valid for all non-turbid beers
The formation of haze is forced through the addition of formaldehyde and storage at 0 °C. The difference in the turbidity formed and the turbidity at the beginning is compared.
This method describes the conditions under which sensory analysis is to be performed.
Beer, beer-based beverages, non-alcoholic beverages, mineral water
One of the fundamental prerequisites for a properly structured sensory evaluation of beverages is training members of the tasting panel.