Investigation of filtration-inhibitory substances in German wheat beer

Although production of crystal wheat beer represents only a small group in German beer market, major problems could be observed during these clarification processes. Because of a proportion of at least 50 % wheat malt, beer composition is not comparable to bottom fermented lager beer. Thus, this study aimed to investigate filtration-inhibitory substances during wheat beer filtration. Besides determination of filterability, beer composition was analysed investigating α-/β-glucans, arabinoxylans, proteins, polyphenols and yeast cell count. Furthermore industrial scale pressure rise at filter inlet and turbidity at filter outlet were determined. Enzymatic hydrolysis of rough beer samples and subsequent membrane filtration observed nearly 55 % increase by degradation of proteins and 45 % degrading hemicellulose ingredients. Significant correlation could be determined between pressure rise and rising yeast cell count (r = -0.635, P<0.05) as well as decreasing iodine value (r = 0.727, P<0.01). Laboratory determined filterability resulted in significant correlation to pressure rise of diatomaceous earth candle filter (r = 0.564, P<0.05). Typical filtration inhibitory substances like β-glucan, arabinoxylan or protein content showed no correlation to laboratory filtration or pressure rise in industrial scale. Obtained results show the impact of wheat malt grist load and its effect on beer composition and filter properties.