Lesson 7 - Wort Separation Process Control SAQ

**When mash separation starts to run slower than normal, which two variables of  Darcy’s Law  are likely to have changed?

Response:

Darcy’s law:

For a given situation, the cross-sectional area A, bed depth L, and ΔP are constant. The two variables that are likely to have caused reduced flow are a decrease in grain bed permeability K and an increase in viscosity μ.

Grain bed permeability will decrease with a finer grind. A plansifter analysis will identify if this is the case.

If we assume no increase in wort gravity, no reduction in wort temperature, and no increase in mash shear, then a viscosity increase will have come from a change in the malt. Reduced malt modification and consequent increased levels of beta glucan/arabinoxylan will increase wort viscosity. The malt certificate of analysis will confirm this if so.