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Getting hands-on with mashing

23 May 2017
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Getting hands-on with mashing


Tips for building mashing equipment

By Michael Trommer

The purpose of the mashing process

After the dissolution of the malted grain components in water, the concentration of certain constituents must reach a certain limit. Those constituents are the products originating from the protein carbohydrate, and all the other organic and inorganic components. These concentrations depend on the type of beer being brewed. They can also ensure that the entire process will run without greater problems throughout all the stages, up to the finished beer.

In other words, during the mashing process, when the ground malted barley is mixed with water, elements of the grain are dissolved, causing the gain of the extract elements.

All the grain elements that dissolve in the water are considered extract. The composition of the constituents mentioned above is determined by the enzymes of the grain itself in ideal pH level, as well as rests done at certain temperatures to allow the work of some enzymes for a particular period of time.

Mashing container

In the infusion method, a heatable mash tun is used. In decoction mashing, there is a smaller pot next to the mash tun, called mash pot, for heating up a portion of the mash.

During the mashing process, the mash tun is used for storage of a portion of the mash at a certain temperature, as well as for pumping the mash to the wort filtration equipment.

The shape of the container may be round, oval, or four-cornered, and made of stainless steel, copper, or carbon-iron covered with stainless steel.

In order to ensure mash storage at a given temperature for a certain period, insulation is required on the sides and bottom of the container. The tun must have a lid, although it does have to be insulated. It is also necessary a chimney for steam venting.

Rock wool, glass wool, or chemical foam can be used as insulation. The insulation material must be covered with a stainless steel plate, which will protect the insulation against humidity. The bottom of the mash tun is cylindrical, slightly conical, and the liquid outlet is located on the deeper part of the tun floor.

Container heating normally is performed using saturated steam or hot water. The heating area is made up of a half-pipe coil jacket. The capacity of the heating area must be calculated to make sure that the temperature of the entire mash, a mixture of malt and water, can be raised 1°C per minute.

For Pilsner beers, 4 to 5 liters of water must be used for every kilogram of malt.

The agitator (stirring paddle) is of utmost importance. It must be assembled so that it does not affect the mash composition, creating difficulties to the wort filtration afterwards or adding acerbity to the finished beer.

Calculation of mash tun capacity or tonnage

For 100 kg of unground malt

400 liters of water

Grist (ground malt)

70 liters

Stirring area
(40%, to avoid overflowing)

200 liters

Total capacity

670 liters (6.7 hl)
of nominal volume

At high speed settings (high rpm), the mash absorbs more air (oxygen). At the ideal stirring speed of the mix, the surface of the wort should remain smooth, without waves or turbulence, and it should not form a funnel shape (whirlpool) inside the mash.

There is a minimum speed (rpm) setting for stirring all the solid particles, keeping them from settling on the bottom. With optimal paddle inclination, the mash is perpendicularly tossed at the center of the tun, over the heated bottom of the tun. The circulation of the liquid creates a convection current in the mash. The current, formed due to the stirring of the agitator, prevents settling or the formation of lumps.

In practice, there are plenty of speed settings available for the agitator, depending on the shape of the tun. For large round tuns plus 5 tons of grist, the speed is 35 rpm for the malt intake and 10 to 12 rpm for the slow stages of the mashing process.

There is also an intermediate speed, of 20 to 25 rpm. In tuns with rectangular corners, the agitator has two speed settings.

In order to ensure homogenization of the malt in the water, the drop chute of the grist case firstly goes into a premasher, and then to the tun, when the grist is already dissolved in water and falls into the tun without dusting or forming lumps. The premasher must be

carefully cleaned in order to avoid moist grist residue, which can sour the mash or affect its pH level.

New theories about mash oxygenation suggest that, to ensure a quality product, the grist and the water should ideally be fed into the mash tun through an inlet at the bottom of the tun.

Mash boiling pot

The mash boiling pot has a smaller capacity than the mash tun. Small amounts of wort are sent from the mash tun to the boiling pot (autoclave). The capacity of the mash pot corresponds to two thirds of that of the mash tun, and it is made of the same material.

In round tuns, the bottom of the pot is slightly conical. The heating area must be calculated so that a fraction of the mash out of one third of the total contained in the mash tun can be heated by 2°C per minute. In some countries, this tun is used for the non-malted adjuncts. The agitator must have a speed setting of 20 to 25 rpm.

In simpler mashing processes, the role of the mash tun is performed by the lauter tun. In order to accomplish that, the rake must have a proper blade speed and inclination to offer a good mixing action. The false bottom must be sealed, to avoid passage of liquid to the filtering chamber.


The function of the mash pot is done by the wort kettle (boiling kettle), which must have a properly adjusted agitator. Since the container holds only a smaller volume of mash, which is boiled before wort clarification, the heating jacket must have divisions so that a smaller heating area is used in this stage.

This concept of mashing with a mash tun and a boiling kettle is used on the decoction method; two containers are used in the mashing process. In the decoction method, part of the mash is boiled, and the rest is left in the mash tun. In the infusion method, only one tun is used: a heated mash tun. The entire mash is kept in the same container. The heating of the mash occurs according to a pre-established temperature ramp, using hot water or saturated steam.

Tips and cares

}} The heating occurs through half pipes welded to the bottom and part of the side of the tun.

}} Many tuns are made of carbon-iron, with an internal cover made with a thin stainless steel plate.

}} The system has steam traps to make sure the pressure inside the hot pipes is constant. That way, the condensate goes through the trap and returns without pressure to the steam-producing kettle.

}} For dark beers, thicker mashes are chosen, with 3 to 3.5 liter per kilogram. The goal is to produce a greater amount of caramelization, in order to lend a richer malt flavor and aroma to the finished beer.

}} Oxygen absorption has a negative effect on the hot mash. It can be reduced through the following:

- grist transference through a screw conveyor;

- performing mashing in the mill;

- mash inlet at the bottom of the tun;

- avoiding the formation of whirlpools during the passage of the mash to the other tun.

}} Little oxygen absorption produces the following results:

- improvement on the break-down of hemicellulose, and consequently a better amide extraction;

- increase on complete fermentation;

- faster filtration in the lauter tun;

- clearer color of the mash and beer;

- improvement on head retention.


Mash tuns may be made of stainless steel, copper, or iron covered with stainless steel

These are fairly solid arguments to reduce or eliminate any incorporation of oxygen from the mashing process.

                         Michael Trommer

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Michael Trommer

Michael Trommer, descendente de pais alemães que vieram para colonização do norte do Paraná e posteriormente migraram para São Paulo.

Com 28 anos de experiência profissional na área de bebidas (cervejas e sucos). Contudo, sua maior atuação foi na indústria cervejeira, onde atuou na área de produção, laboratório, desenvolvimento de produtos maltados e não maltados, padronização de processos (sistema da qualidade) e implantação de manutenção preventiva e preditiva. Presta serviços para empresas de pequeno, médio e grande porte do segmento de bebidas.

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