Determination of Cytolytic Malt Modification–Part II: Impact on Wort Separation

The cytolytic malt criteria viscosity and β-glucan are used as an integral part of routine laboratory control measures to classify the malt modification level and to ensure good processability. Part one of this two-part publication demonstrated that barley varieties with high cytolytic modification along with low β-glucan content tend to have a higher content of usually unconsidered water-soluble arabinoxylan. This study investigated the arabinoxylan molar mass distribution and its impact on processability. In order to observe the impact of arabinoxylans on separation processes in the brewhouse, lautering tests of different modified malt types were performed. The results suggest that in contrast to their lower β-glucan content, highly modified malt types had a higher average arabinoxylan content (767 mg/L) than medium modified samples (710 mg/L). Furthermore, differentiation of arabinoxylan molar mass resulted in a higher molar mass of 14–34% above 50 kDa in these samples. In terms of processability, flux through the spent grain cake was mainly influenced by wort viscosity (r=-0.621, p < 0.01), although arabinoxylan had little influence on the viscosity. However, 53% of highly modified malt samples had a flux of less than 4 L/h × m² (average value) despite low β-glucan levels. A principal component analysis identified arabinoxylans as the main driving force in connection with the permeability through the filter cake, whereby especially highly modified barley varieties (60%) were affected. Arabinoxylans may have a decisive effect, so it is not only β-glucan as a structural cell wall substance and present viscosity that should be considered as determining quality characteristics.