The chemistry behind the Falling Number® method

When the tubes are placed in the boiling water bath, the starch begins to gelatinize and the slurry becomes more viscous. The mixing makes sure the gelatinization is homogeneous in the slurry. What also happens at this elevated temperature is that the alpha-amylase enzyme starts to break down the starch and the viscosity thus decreases. The amount of starch break-down is dependent on the alpha-amylase activity and this means that the higher the activity of the alpha-amylase the lower the viscosity will be. When the stirrer is dropped, its speed and thus the time it takes it to fall to the bottom, will be determined by the viscosity of the slurry.

In other words, the more sprouted the grain was the higher the alpha-amylase activity will be. The higher the alpha-amylase activity the lower the viscosity of the slurry. The lower the viscosity of the slurry the faster the stirrer will fall to the bottom. That is why more sprouted grain results in a lower Falling Number® as Falling Number® is the time it takes the stirrer to fall to the bottom.