Great technique for improving mash efficiency
During the mash, enzymes attack complex carbohydrates in the grain and break them up into more simple sugars that yeast can digest. If all (or most) of the available complex carbohydrates are modified by the enzymes and extracted in the wort, a 'high efficiency' is achieved. If much of the total available carbohydrates remain in the grain and are not extracted to the wort, a 'low efficiency' is achieved. An extraction of greater than 70% of total sugars into the wort is considered good, with above 80% considered high.
While many factors play a role in mashing (see this article for more), mixing of the grain in the water at the start of the mash period is important to high efficiency. Enzymes need water for accessing the carbohydrates so a thoroughly wet and fluid grain bed is important for maximizing the exposure of enzymes to the carbohydrates. If the grain is not thoroughly wet and clumps of dry grain exist (sometimes referred to as 'dough balls') mash efficiency will be lower as the enzymes will not be able to access the carbohydrates in the dry grain. Similarly, if the grain bed is compact, water will not move easily around the grain and enzymes will access the carbohydrates only very slowly—this also will contribute to poor or low efficiency as only a smaller percentage of total sugars in the grain will end up in the wort. (This is why a proper crush size is so important. A small crush results in a high surface area and better exposure of the complex carbohydrates in the grain, but leads to more compaction and 'stickiness' in the grain bed. A large crush size is very fluid and harder to compact, but has less surface area and therefore poor exposure of the complex carbohydrates inside the grain. A good compromise is a crush size of 1.1-1.2mm/0.043-0.048" which opens up the grain without pulverizing it. The picture on the left shows a good crush. See a high definition image on this page.)
Properly mixing the mash is necessary for wetting the grain and creating as 'light' a grain bed as possible for good water/wort circulation. Our Mash Mixers are the very best tool we have found for gently mixing the mash thoroughly and properly setting the grain bed. And being operated by a drill is faster and easier than a mash paddle...and without the blisters.
Other tips include not adding the grain too fast (which then requires excessive mechanical agitation which ironically can end up with a more compact bed), adding toasted or dark malts after the light malts to keep them near the top of the grain bed (they tend to fragment more when crushing and will be more gummy), not overmixing the grain when mashing in (mix just enough to remove air pockets), and not moving the mixer near the false bottom on the Colander as this can force grain into the bottom (perforations or wedge wire) and plug it up. When mashing with the wedge wire false bottom (all MB Colanders), prior to adding the grain, connect the pump line and open the bottom valve to release air bubbles in the line, then tap the wedge wire to release any air bubbles that are trapped under the wedge wire.