Pearling barley to alter the composition of the raw material before brewing

Abstract

Partly replacing malt with unmalted barley is a trend in brewing. The use of unmalted barley, however, leads to issues such as haze and high mash viscosity, due to its higher content of undesired components. Pearling, an abrasive method to remove the outer layers of the barley kernels has been shown to reduce the content of insoluble fibre, ash, protein and polyphenols; the β-amylase activity and starch content of the remaining kernel were hardly affected. Removing the outer 5% of the kernel, for example, results in a 15% reduction of insoluble arabinoxylans, 23% of the insoluble fibre content and 25% of the water holding capacity of the non-starch components. It also reduces the ash content by 19% and the polyphenol content by 11%, but only 0.20% of the starch is pearled off. A relation was found between the insoluble fibre content and the water holding capacity of a fraction. Lower fibre content reduces the water holding capacity and thus the volume of the spent grains, which implies that less wort and sugar are lost during filtration. In addition, that the bran fraction remains dry, implies a reduction in energy required to dry the spent grains.