Four ways to improve mash efficiency
Mash efficiency refers to the extent to which you are able to pull the sugars out of the malted grain and into the water. If a high percentage of sugar is recovered (75-90%) into the water, it is called high mash efficiency. A low percentage (60-75%) is called low efficiency. Since the amount of sugar in the water correlates quite closely to the amount of alcohol you will have in the beer, it is important to understand mash efficiency in order to produce consistent results.
A low efficiency can be compensated for by increasing your grain bill (the amount of malted grain you start with). For example, if your mash efficiency is at 70% resulting in an alcohol content of 4% in your beer, you can increase your grain bill by 20% to bring the sugar and alcohol content higher. But this also adds cost to your brewing as the extra grain costs money and with more grain, you need a larger mash tun which also adds cost. The best way to increase mash efficiency is through proper technique.
In addition to using fresh grain, having a proper crush size and correct water chemistry, there are four actions to increase efficiency.
The first action is to properly mash in by thoroughly mixing the grain with the water. Clumps of grain and air can easily form when mixing the grain with the water. These clumps prevent water from accessing the crushed grain inside the clump, preventing the carbohydrates from being dissolved into the water and preventing enzymes from breaking the carbohydrates up into sugars that the yeast can digest. It is important to ensure that these clumps are completely broken up and a proper grain bed forms. The BREWHA Mash Mixer is an easy and effective way to mix the mash.
The second action is to closely regulate mash temperature. The enzymes that work to cut up carbohydrates into smaller sugars that yeast can digest (in the process called 'saccharification'), producing CO2 and ethanol (alcohol) in the process, work best at specific temperatures. If the mash is not kept at the precise temperature the recipe calls for, optimal, consistent efficiency will not be achieved. The first step to ensure the proper temperature is to ensure the strike temperature is sufficiently high. Since the grain addition will cool the water, the temperature of the water before adding grain should be above the mash temperature. Grain will generally cool water by 5-8C/10-15F so the strike temperature should be that much higher. After mashing in, check the temperature in the grain bed with a thermometer to ensure the strike temperature was high enough. The mash temperature can be easily regulated with BREWHA vessels since the mash tun, hot liquor tank and BIAC have built in ports for heating elements and temperature sensors to precisely control the temperature of the mash.
The third action to increase mash efficiency is by using a recirculating pump (Figure 1). The pump pulls wort (sugary water) out of the bottom of the mash vessel (past the heating element under the mash screen) and puts it back into the top of the mash vessel above the grain bed. This circulating action provides movement of the enzymes and water past the crushed malted grain resulting in more even temperature throughout the gain bed and greatest interaction of the enzymes and grain carbohydrates, leading to greatest efficiency. When circulating with the pump, the return flow back into the mash vessel should be throttled with a valve to ensure the grain bed is not compacted as this will impede saccharification and could damage the heating element. If the wort level is rising at the top of the mash vessel, it indicates that too much volume is being moved by the pump and the flow should be throttled with the valve (install valve ONLY on downstream side of pump either on pump exit or on the Mash Colander port). If the wort stops moving down through the grain bed (or moves only very slowly) it likely means the grain bed is compacted and needs to be stirred up and reformed. If the pump plugs frequently when using the BIAC, the hose from the fermenter to the pump can be attached to the side racking port (instead of the bottom) to prevent grain from being drawn into the pump.
The fourth action is to slowly sparge the grain prior to lautering. The tendency at the end of mashing is to want to hurry the lautering and rush into boil. This is a mistake as far as increasing efficiency is concerned. Residual sugars inside the grain do not immediately flush out with fresh water but slowly diffuse out. If not given sufficient time (around 60 minutes is not too long) they will remain in the grain and recovery of sugar will be decreased.
With an appropriate mash period (60-75 minutes is typical), proper crush size and water chemistry and by observing the above actions, consistently high mash efficiency can be achieved.