Lesson 6 - Mashing Technology

The mash heating system works in collaboration with the agitator to heat the mash evenly and effectively. As with the other technologies, designs range from very basic to technically advanced.

What does mash heating need to do?

1. Transfer heat into the mash effectively

2. Supply the required rate of heating to achieve the temperature ramps in the programme

3. Minimise fouling of the heating surface

4. Minimise overheating of mash adjacent to the heating surface

Before we dive into the technologies, it is important to highlight the importance of agitation during mash heating. If you have ever tried putting a cold pan of baked beans onto a stove and heating them without stirring, you will know that you get tepid beans and sauce on the top and a smoking crust of burned beans on the base of the pan. Something less dramatic but no more desirable would occur if we heated a mash vessel without agitation.

Effective agitation is essential to increase the rate of heat transfer from the heating source and to distribute the heat supplied evenly through the mash.

So, what methods of mash heating are used? They are:

• Direct flame heating

• Heating jackets (and in a few breweries, heating coils)

• Steam injection

Direct flame heating

Although called direct flame heating, the flame does (should) not play on the base of the vessel. Instead, the combustion products of the gas or oil burned are passed under the vessel or through heating coils or jackets. This heating technology is only used for small batches and in smaller breweries or very old ones. Due to the very high temperatures of the combustion products, direct flame heating is very difficult to control to achieve slow temperature increases. Therefore, it is more suited for use in decoction mash kettles than to MCVs for single-vessel temperature-programmed mashing.

Direct flame heating usually causes the mash to burn onto the outside of the vessel and gives uneven temperatures through the mash. The high temperatures also cause stress corrosion of the vessel materials of construction, meaning they do not last as long as vessels heated by steam. There are much safer, more effective and energy-efficient ways to heat mash!