Lesson 4 - The Mashing Process
This lesson discusses the process of mashing. It provides an overview and sets out the objectives of the process before explaining what parameters need to be controlled to ensure success. It describes the various methods used to mash and their impact on the wort produced. Finally, it details the composition of wort produced by mashing.
Oxygen and Mashing
Oxygen has been called beer enemy number one. It is also the enemy of the mash. Oxidation of the wort during mashing has been linked to accelerated beer staling after packaging. So, for all but short shelf life (cask or tank) beers or beers destined to be matured in wood or intentionally oxidised, control of oxygen in mashing is essential.
The chemistry of beer staling by oxygen is complex and not yet fully understood. However, we do know that if oxygen isn’t there, it can’t do any harm. So, when we say control, what we actually mean is exclusion! We must do all we can to limit oxygen’s access to the mash. Here are some measures that we can put in place to exclude oxygen:
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Fill vessels from the bottom
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Purge oxygen from the mill, conveyor and vessels using CO2 or nitrogen
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Mill the grist in an oxygen-free environment
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Use deoxygenated mashing water
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Use low agitator speed when mixing the mash
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Use low pump speed when transferring mash
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Design pipework to avoid sharp bends that cause shearing of the mash
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Do not allow the pump to run dry at the end of mashing by chasing out mash with deoxygenated water
Most large modern brewhouses are designed to achieve all of the above. More on this in the Mashing Technology lesson.
Now we have a good appreciation of the factors that affect the mashing process, we can move on to discuss the ways in which we actually mash. Let’s move on and cover the methods of mashing.