Application of the rapid visco analyser as a rheological tool for the characterisation of mash viscosity as affected by the level of barley adjunct

Abstract

The application of the Rapid Visco Analyser (RVA) as a laboratory scale rheological tool for the characterisation of mash viscosity is the subject of this study. Studies were conducted to simulate an industrial mashing process, taking into account temperature/time, grist loads, adjunct amounts and enzyme levels. The RVA was used to characterise the effects of different ratios of malt : barley adjunct. The method was found to have the ability of not only detecting the major viscosity changes which occur during starch gelatinisation/liquefaction processes, but also the minor viscosity changes which were found to occur during the proteolytic and saccharification steps. Clear correlations were found between the level of barley adjunct and the output rheological data points of the peak viscosity at 50°C (PV50, R2 = 0.9931), the rate of viscosity breakdown at 50°C (BR50, R2 = 0.9522), the peak viscosity prior to gelatinisation (PVG, R2 = 0.9988), the area recorded under the gelatinisation curve (PGA, R2 = 0.9928) and the peak viscosity breakdown rate (VBR, R2 = 0.9783). The developed RVA rheological method is a useful tool for characterising grain quality (adjunct level) with regard to macromolecular viscosity compounds and the grains endogenous enzymatic capabilities. © 2005 The Institute of Brewing & Distilling.