Water intended for use in beer brewing as well as in the production of other foods
Steam-volatile phenols form by bonding with diazotized p-nitroaniline azo dyes; the intensity of the resultant color is measured photometrically following extraction with n-butanol.
The intensity of the color, based on a saturation threshold of phenol of 100 %, is as follows:
phenol 100 % m-xylenol 52 %
o-cresol 147 % p-xylenol 92 %
m-cresol 120 % guaiacol 165 %
p-cresol 21 % pyrocatechol 29 %
o-xylenol 16 % α-naphthol 23 %
This method is suitable for wort, beer and other beverages.
Anthocyanogens adsorb onto polyamide, and this adsorbate is dissolved in butanol hydrochloric acid and heated, causing a red color to develop, which is then measured spectrophotometrically.
This method is suitable for (bottom-fermented) beer and beverages.
The fraction of phenols extracted using steam are converted to color complex using 4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (4-aminophenazone) in an alkaline medium and through oxidation with potassium ferrocyanide (III), which can be measured spectrophotometrically after extraction with chloroform (fig. 1).