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Mashing
Mashing involves the mixing of the grist with hot water to form a mash in which the natural malt enzymes will break down the malt starch into sugars.
This is carried out using a screw conveyor, which pulls the grist from a sliding gate in the bottom of the grist case. As the grist is carried along the conveyor hot liquor (brewing parlance for water) is pumped into the conveyor and the two mix together to form a mash which looks very similar to coarse porridge.
At the end of the conveyor the mash drops into a large vessel called a “mash tun” where the mash is collected.
The temperature of the mash is critical and is achieved by controlling the “striking heat” or temperature of the liquor and ensuring the mash tun is pre heated before mashing begins.
The mash temperature normally lies in a range between 62 and 65 °C. As a rule of thumb a lower temperature will produce an extract of more fermentable sugars while a higher temperature will produce a greater extract but will tend to be less fermentable.
The mash is allowed to stand for one hour during which time the malt enzymes break up the starch molecules into fermentable sugars: glucose, maltose, maltotriose, and these sugars dissolve in the liquor surrounding the mash to form a sugary solution called wort.
At this point the wort is run off from the mash tun into the small underback from where it is pumped into one of the two “coppers” or wort kettles.
The bulk of the mash is held back by a false base in the mash tun made up of slotted plates which allow the wort to run through to four outlets spaced across the base each terminating in valves above the underback.
This run off process is carried out slowly over 2 to 3 hour depending on the size of the brew and it is at this point that the importance of not milling the malt too finely comes in. If the grist is too fine it becomes very difficult to separate liquid from the mash. How ever if the husks are more or less intact the mash remains open during run off, allowing a good separation.
