Influence of germination time and temperature on the properties of rye malt and rye malt based worts

The effects of germination time and temperature on the quality of rye malt and worts derived thereof were investigated using Response Surface Methodology. Amylolytic and proteolytic enzyme activities were increased by long germination periods, while β-glucanase activity was not influenced. Total and Soluble Nitrogen content were also not significantly affected by the variations in germination conditions. Free Amino Nitrogen (FAN) was found in higher amounts in worts prepared from rye malts with long germination times. Extract contents were higher in rye malt than in the control barley malt and could be increased by a favourable germination regime, while no such impact on wort fermentability was found. High wort viscosities could be significantly reduced by a long germination period at low temperatures, but were still unacceptably high. The same conditions favoured the development of endoxylanase activity. Arabinoxylan (AX) accumulated during the germination process and their extractability increased. The results suggest that longer germination periods resulted in an increased number of AX molecules with lower molecular mass. Optimal rye malt qualities within the limits of this study were found for a germination time of 144 h at 10 °C, which resulted in an acceptable FAN content and the lowest measured viscosity.