Quality control of malt: Turbidity problems of standard worts given by the presence of microbial cells

Abstract

Since the main effect on beer colour originates from the chemicalcomposition of malt, the measurement of the colour of wortobtained from malt is one of the most important quality parametersto be controlled. Malt colour determination is usually performedspectrophotometrically on EBC Congress worts, whichare generally bright. The quality control on the malt harvested inthe year 2007 highlighted a problem of turbid Congress wort, fora part of Northern Europe samples analyzed, and therefore thespectrophotometric determination of the colour of wort was notpossible. Thus both analytical screening of the quality parametersof malt and the scanning electron microscope (SEM) wereused to identify the nature of the turbidity in the worts. The resultsobtained suggested that the nature of the turbidity of Congressworts could have been due to microbial contamination ofthe barley, enhanced in particular by the rainy harvest and theconsequent formation of exopolysaccharides (EPS) by stressedyeast and bacteria during malting. © 2011 The Institute of Brewing & Distilling.