Eight 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.
First, it is important to ensure is that your ingredients are fresh. The yield will be lower with oxidized/stale grain.
Second, it is important to have a proper crush size and properly crush the grain. For most systems, a crush size of 0.04" (1mm) is the best (if routinely seeing a stuck mash where wort will not flow through the grain bed, one solution can be to increase the crush size slightly). It is also very important that grain be 'crushed' and not 'ground'. Grinding involves shearing of grain into fine particles (that gum up), whereas crushing sends cracks throughout the grain that open up to insides of the grain to water and enzymatic digestion. A 3 roller mill generally provides a better crush than a 2 roller mill, and the speed of the mill is also very important to maintain. The mill rollers should rotate at about 150rpm, whereas most electric drills operate at 600-1800rpm. Pulleys can be used, or a simpler solution is to purchase a variable speed drill and use it on a low setting. If the drill is a manual type (where depressing a button manually will be tiresome and inconsistent) it can be helpful to use a '120V fan speed controller' (google that) to control the drill speed to 150rpm (if it is hard to calculate the speed, put a piece of visible tape on the drill chuck and count the number of times it passes each second—it should be close to 3/second). If the drill is not strong enough to turn the mill on low speed, the grain intake inside the hopper can be restricted to let less grain through at one time—it will take slightly longer but your crush will be more effective.
A third step is to ensure proper water chemistry. Water chemistry is a complex topic which we won't get into here, but if you suspect water issues, try brewing with bottled (spring or RO) water that you know is neutral and compare results.
Fourth, ensure mash pH is around 5.2-5.3.
Fifth, 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.
Sixth, 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 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 seventh tip for increasing mash efficiency is by stirring or 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. Check your temperature of the returning wort to ensure it is not cooling the grain bed—particularly with a Small mash tun/Colander, the return rate needs to be very slow, and cooling can occur in the hose; if this occurs, the temperature of the wort entering the hoses should be raised a degree or two. 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 the valve ONLY on downstream side of pump either on pump exit or on the Mash Colander port or the pump will not work properly). 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 (due to grain falling to the bottom of the fermenter and entering the pump hose), 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. With a very thick mash, channeling of the wort down through the mash may occur so use of the Mash Mixer at regular intervals to disrupt the top 4/5 of the mash bed can be helpful.
The eighth 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 to sparge and lauter 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.