W-000.37.002 [2005-08] Steam-volatile Phenols in Water
Application/Purpose
The method describes how to determine steam-volatile phenols in water.
Steam-volatile phenols comprise groups of compounds including phenol, cresols, xylenols, guaiacol, thymol, the main part of pyrocatechol and a small part of α-naphthol. They are the most significant among the phenols regarding impairment of the odor and flavor of water. In particular, halogen derivatives exhibit a very intense odor and flavor (sometimes referred to a pharmacy odor or medicinal odor).
Scope of Application
Water intended for use in beer brewing as well as in the production of other foods
Principle
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 %