What is Mashing Efficiency and how to calculate?

Mash efficiency is simply the percentage of “potential” sugars that are extracted from the grains during the mash. It is typically a percentage in the 80% range. If we take the “potential” points of the grains, and multiply it by this percentage we get the points extracted from the mash.

Each individual grain used has its own “yield.” The yield is a percentage that represents the percent of the weight of the grain that can be converted into sugar under ideal laboratory conditions. An average pale malt might have a yield of about 80 percent, meaning that 80 percent of the sugars could be converted and extracted in an “ideal” laboratory setting.

A real-world brewing system outside of a laboratory does not achieve this perfect number. In fact, a typical brewing system is only going to get perhaps 80–90 percent of the potential sugars extracted during the mash, meaning that 80–90 percent of the yield will be achieved, coming directly from the mash tun. It is called as a mashing efficiency.

So, then let's think... It is 80% to 90% from the mashing of the 80% of the potential extracted sugar from the grains (in this case 80% refers to the yield of a pale malt).

The portion of the “ideal” number that the system extracts during the mash phase is called the mash efficiency.

Of course, the mash itself is only one step in the brewing process.

Possible losses in the complete Brew process...

• Before mashing you have the grinded grains, that can affect the sugar extraction during the mashing.

• During mashing you have the specified temperature range, water/grist concentration, water pH, etc.

• After mashing, you can add sparging water, sugar. boil, chill, and transfer the wort, all of those small sub-processes can results in some further losses. "trub" loss, chilling, and transfer losses into the fermenter.

All of these losses result in a lower original gravity of the wort into the fermenter.

The overall efficiency of the system from grinding grains to the gravity points going to the fermenter is called the Brewhouse Efficiency.

It represents how well the complete brewing system converts potential sugar from the raw grains into original gravity points (sugars) in the fermenter. This number is always lower than the mash efficiency due to the additional losses in these later steps and it is typically in the 65% to 75% range for many homebrew systems.

Calculating Mash Efficiency

Mash efficiency is a measurement of the percent of available sugars obtained through the mashing process. Brewing malt contains a certain amount of complex sugars, and the percentage which are extracted in a mash give us the mash efficiency.

By improving mash efficiency means we can use less malt and save a little money, but the real value for the homebrewer is the ability to accurately predict the amount of malt needed when formulating a beer recipe.

Calculating mash efficiency, by using the gravity measurement of points per gallon (PPG):

Suppose we use 10 pounds (4,5 kg) of two-row malt in a mash, and that this malt has a gravity rating of 1.037, or 37 points. After the mash and the sparge, we end up with 5 gallons (19 liters) of wort.

If we were to extract all of the sugars from that malt (achieving 100% efficiency), the resulting wort would have a total of 370 points (37 points * 10 pounds). Divide by 5 gallons, and the resulting pre-boil gravity would have 74 points per gallon, or a gravity of 1.074.

But even the most efficient mashing processes can’t extract all of the sugars from the malt. The typical mash efficiency of a homebrewer will be in the ballpark of 60-80%, though this number can vary quite a bit depending on the brew, the type of homebrewing equipment being used, and number of other factors.

Continuing with the example above, suppose that the actual measured gravity of the wort when taken by a hydrometer is 1.050. We simply divide the measured gravity by the potential gravity to calculate the mash efficiency:

50 / 74 = 0,6757 = 67,6%

The challenging part of calculating mash efficiency is that we tend to brew with multiple types of malts, often with different extract ratings. As a result, calculations become a little more complicated.

Suppose we mash the following grain bill and end up with 5 gallons (19 liters) of wort:

• 8 lbs. (3,6 kg) two-row base malt (1.037)

• 2 lbs. (1 kg) Munich malt (1.033)

• 1 lbs. (0,5 kg) Crystal 60L malt (1.034)

Our total extract potential is:

[(37 * 8) + (33 * 2) + (34 * 1)] / 5 = 79.2

If our measured pre-boil gravity is 1.060, then our mash efficiency is calculated in this way: 60 / 79.2 = 75.8%

That’s actually a pretty good efficiency!

Improving Mash Efficiency

Beginning all-grain brewers may find that their mash efficiency is in the 50-60% range. With consistent note-taking, mash efficiency can be improved in the following ways:

• Better grain crush. If grain isn’t crushed enough, it will be difficult to extract the sugars from the grain. On the other hand, if the grain is crushed to much, the brewer risks a stuck sparge. It’s important to set the grain mill to get an appropriate crush.

• Improved mash procedures (appropriate pH, temperature, water-to-grain ratio, length of mash)

• Appropriate water chemistry

• Improved sparge techniques – A slower sparge (30-60 minutes) will rinse more sugars from the mash than a fast one. Sparging with too much water will decrease your mash efficiency.

All of the above are effective ways to improve your mash efficiency. Get a handle on them and you’ll get more sugar from your grains.

Many new all-grain brewers struggle with low efficiency numbers, resulting in lower- than-expected original gravity for their beer. Some of these inefficiencies can be corrected through experience. As you become more familiar with all-grain brewing, your efficiency will often improve.

Another solution is to simply lower the brewhouse or mash efficiency estimate you are using to develop your recipes. This will effectively cause you to use a bit more grain in your recipe but should allow you to hit your original gravity with only a dollar or two of extra grain added per batch.

If you truly are experiencing low efficiency in your batches, the next item I recommend looking at is your grain crush. The crush of the grain can have a huge impact on the efficiency you will see from your brewing system. I’ve had cases where a grind that is too coarse, often from grains crushed at a store, can result in low gravity numbers.

The ideal grain crush is actually pretty fine. The inside of the grain should be crushed to fine granules, but you should still have large pieces of the grain husk left intact to act as a filter bed. It is a delicate balance, however, for if you crush the grains too finely you can end up with a “stuck sparge” that will gum up your mash-tun filter and prevent proper lautering.

If you have properly crushed grains, then the next item to look at is your sparging/lauter process. Make sure you are sparging with hot water at the proper temperature. The sparge water should be at least as hot as your final mash step, though it is not uncommon to sparge with slightly hotter water to improve the viscosity of wort during sparging and extract more sugar.

Also, in general, a slow sparge will extract more sugars than a very fast one, so try taking your time during the sparge phase to slowly draw wort from the bottom of your mash tun. In some cases the design of the mash tun can play an important role as well—ideally you want a mash filter that covers the entire bottom of the tun so you can draw wort off evenly and avoid channeling in the grain bed. Finally, look at losses in every phase of your brewing process. Wort lost below the mash-tun spigot, in transfers, in your chiller, in the trub left in the boiler, and even in hoses or pumps represents lost sugars and will lower your overall efficiency. Reduce losses whenever possible for a more efficient brewing system.