Lesson 7 - Mashing Technology SAQ

**Select the best mashing technology for the following scenarios and explain your choices:

a)    A brewpub with very little money for equipment that only sells draught beer.

b)    A ten million hL per year brewery making international lagers from under-modified malt and 30% rice grits, to be packaged into bottles for export.

Response:

a) For this option we are limited in how much we can spend and also in terms of the space we have for the equipment. We, therefore, need a very simple set-up. Fortunately, shelf life is not a concern as the beer will be sold on-site, so we do not have to worry too much about oxygen control. That said, we should still try to minimise oxidation. To minimise the number of vessels we are using, we can opt for a mash tun and isothermal mashing. This also removes the need for dedicated mash transfer pipework and a mash pump.

Although money is tight, installing grossly, inefficient equipment/processes should be dismissed as an option. Therefore we should not consider trying to mash in without a pre-masher. Even with a small vessel, manual agitation of grist poured into a mash tun full of water is likely to provide uneven hydration, leading to inconsistent extract recovery, which will cause inconsistent beer. Pounding the mash with paddles can lead to mash particles being forced through the false bottom of the vessel, which can slow wort separation. Instead, a simple cone pre-masher could be used. If operated at the correct flow rate of water and grist, these can produce an evenly hydrated mash that is not saturated with water. The flow at mashing in would be directed to the centre of the mash tun to help produce an even mash bed.

b) The set-up required for this application couldn’t be any more different to scenario a). We need technology that will:

• Gelatinise starch with a higher temperature than that of barley large starch granules

• Enable cytolytic and proteolytic enzymes from the malt to work at their optimum temperatures.

• Minimise oxygen pick up so as not to reduce product shelf life

• Minimise shearing of mash to ensure rapid wort separation

• Maximise extract recovery

• Achieve all of the above in the shortest time possible

The wort separation technology that provides the best extract recovery in the shortest time is the mash filter. We don’t discover this until we cover wort separation, so we should also consider preparing the mash for a lauter tun.

Pre-mashing

The best technology for minimising oxidation and shear for mash filters is a CO₂ aspirated hammer mill feeding a Mechamasher. For a lauter tun, it is a wet mill. Both of these technologies feed from the bottom of the MCV and cereal cooker (we wouldn’t use the wet mill for the grits).

Cereal cooking

The rice grits will need to be cooked in a separate vessel from the malt mash, so we have the option of using a dedicated cereal cooker that would be smaller than the MCV or to use a separate MCV for the task. It is likely with a brewery of this size that there will be several brews underway at any one time, so we could cook the rice grits for two or three brews in one MCV to save energy and space. This would rely on effective scheduling/coordination of brews because neither the MCV nor the cereal cooker are vessels in which you can leave a brew for a while without experiencing problems. For example, excessive thermal load, starch retrogradation and excessive proteolysis can occur if mashing time is extended.

MCV

If we did not have the ability to generate culinary steam, the MCV would be heated with dimple jackets because these achieve the best heat transfer. The dimples would be in contact with the mash to enhance heat transfer. Hot water injection could be used to raise the temperature from proteolysis to saccharification as this is more rapid than jacket heating and optimises mash thickness for both stands. If we could produce culinary steam, we would use direct steam injection to minimise shear oxidation and heat up time. Low shear mixers would be used in both scenarios, with the mixers in the jacketed vessel used to move the mash over the heating surface and those in the steam heated mash used to stir the body of the mash.

Mash transfer

Mash would be transferred down lines flushed with deaerated water using a pump running at < 1,000 rpm at a velocity of less than 1.5 m/s. The pipework and pump would be large enough to move the mash as quickly as possible without exceeding these levels. The limit of flow should be a gentle filling of the wort separation device and not a constraint of the pump or pipework. The pipework would also be as free as possible from bends and obstructions. Any bends would be gentle and sweeping.