Starch properties of malted barley in relation to real degree of fermentation

Real degree of fermentation (RDF) is an important measure of brewhouse performance in the production of beer. In this work, the relationship of RDF with malted barley starch properties was investigated. Starches were isolated from 25 malted barley samples and analyzed for molecular size distribution (by HPSEC), AP structural features (by high-performance size exclusion chromatography with multi-angle laser light scattering and RI detectors), and thermal properties (by DSC). Cluster analysis, analysis of variance, principal component analysis, bivariate correlation, and multiple linear regression analysis were used in establishing correlations. RDF, AM, and AP content were 74.0-80.1%, 25.2-34.4%, and 65.6-74.9%, respectively. Starch gelatinization enthalpy was 6.4-8.1 J/g, and onset gelatinization temperature was 58.5-64.3°C. AP and AM content had a positive and negative impact on RDF, respectively. The effect of thermal properties (starch gelatinization and AM-lipid complex melting) on RDF was not clear. Starch properties explained up to 86% of RDF variance to indicate that other malted barley constituents and/or properties also contribute to cultivar variations in RDF.