This method describes how to determine the steam-volatile phenols in malt.
The degree that whisky malts are smoked is determined by the measurement of steam-volatile phenols. For beer production, smoked malt is used in limited quantities in Germany exclusively in Rauchbier (smoked beer), a Franconian specialty, as well as in other countries for specialty beers. However, technical disruptions during the kilning process can lead to malt that is intended for use in normal beer production, but which possesses a smoky flavor. This smoky flavor is detectable in the beer, and will almost certainly prompt complaints from consumers.
Aside from a sensory evaluation, the best method for determining steam-volatile phenols has proven to be spectrophotometric analysis. This analysis can be used to establish which malt lot is responsible for the smoky flavor and to what extent beer in tanks or packaged beer is affected.
Barley malt (pilsner malt) and smoked malt intended for use in beer brewing or elsewhere in the food industry
The phenol fraction collected through steam distillation is mixed with 4-amino- 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (4-aminophenazone) under alkaline conditions and oxidized by potassium hexacyanoferrate(III) to form a pigment (fig. 1), which after extraction with chloroform, can be measured spectrophotometrically.