A mathematical model describing the effect of the mashing temperature program on dissolution and hydrolysis of β-glucans is presented. In the model, dissolved β-glucans are degraded by dissolved β-glucanases in the liquid phase. Increasing mashing temperature increases the amount of soluble β-glucans in the malt grist phase. Measurements from laboratory scale mashings with different temperature profiles were used for the estimation of the model parameters for a malt produced from the Finnish barley variety Kustaa. The differences between the predicted and measured wort β-glucan concentrations at the end of mashing were 0.04-0.12 g litre−1 in laboratory scale mashings with different malts and in an industrial scale mashing experiment. β-Glucanase activity in the liquid phase during mashing could be predicted with sufficient accuracy in all cases analysed. The simulation results showed that the lowest β-glucan concentration was achieved when the mashing-in temperature was 48 °C.