Calculating Potential Extract from Malt COAs

How much sugar (extract) can we get from malt? When we first start learning to brew the numbers seem like magic and try out best to use what our software or lookup tables (such as those in Palmer’s “How to Brew”) for granted. It’s possible to generalize a grain into one of the known categories, but with the rise of new malts and craft malsters those assumptions may end up being further off than expected. The end result? Missing gravity targets. However, calculating potential extract is quite straightforward and only requires a little bit of math.

Understanding a Malt Certificate of Analysis

Screenshot 2019-05-24 06.52.25

Weyermann Certificate of Analysis for Colonge Malt

In the above Weyermann COA we can see they include a lot of information that brewers can use to understand how a certain malt lot may impact brewhouse performance. In order for us to calculate the potential extract we are interested in two items: moisture content, extract and fine grind – coarse grind difference.

In the above certificate we are lucky because the malster has provided us with the extract brewers are concerned with; extract dry basis. The terminology for this field can vary from maltster, it’s also sometimes known as extract coarse ground, dry basis. In either case, we want to be working with the dry basis (db) extract and can work backwards from there. As you might guess, the dry basis extract isn’t what we can expect from our grain because there’s still some moisture trapped in the malt. This moisture provides no extract whatsoever, so we will need to calculate what the actual extract of the malt will be. With this information we will be calculating percent extract coarse grind, as is (%extract cg, ai).

We also need to know what the fine grind to coarse grind difference is, which can sometimes be included on the certificate of analysis. The reason for the difference is because malsters perform their lab mashes (also known as the congress mash) on very finely crushed grain. This doesn’t represent the real world because mashing with such highly crushed grain would clog up lauter tuns! Some malsters may provide the difference, however it’s not always provided. Usually the difference between a coarse grind and fine grind won’t be more than 2% extract. A rule of thumb one can use 1% as the fine grind to coarse grind difference

%extract gc,ai = %extract cg,db x (1 - %moisture)

From the Weyermann Colonge malt we have the following numbers:

  • %extract (fine grind) dry basis: 81.6%
  • %moisture: 4.2%
  • fine grind – coarse grind difference: unknown; use 1%
%extract cg,db = %extract fg,db - 1% = 81.6% - 1% = 80.6%
%extract cg,ai(WEY Cologne) = 80.6% x (1 - 4.2%) = 77.21%

So what does this mean? We now know that from every unit of Weyermann Colonge malt we will get 0.7721 units of extract (sugar) out of it.

Converting Extract to “Homebrew Units”

In the homebrew world, we don’t typically work with percent extract when building a recipe. With the rise of brewing software, it’s probably even rarer for people to even use homebrew units! However, some software still requires users to enter data as homebrew units for new sources of extract (sugars, malts, adjuncts, etc).

The most common homebrew unit is ppg which stands for points per pound per gallon. There’s another unit that metric users can use called the pkl which stands for points per kilogram per litre. It’s possible to actually calculate out how many ppgs or pkls one would get from their malt however there is an easier way to do it. There’s an adjunct that provides 100% extract and is very well documented in homebrewing books; sucrose!

ppgSucrose = 46
pklSucrose = 384

With the known maximum for our homebrew unit of choice, we can figure out what our potential extract will be:

ppgWeyColonge = 46 * 0.7721 = 35.5 (1.036)
pklWeyColonge = 384 * 0.7721 = 296.5

Adding a New Malt to Brewing Software

This will vary depending on the software one is using, some applications may require the coarse grind dry basis extract and moisture, while some applications may just require extract coarse grind as is. The other possibility is that the ppgs will need to be calculated and that is what is added to the software. With what was previously covered, it’s now possible to fill in any of these gaps!

For this example, the Weyermann Colonge malt will be added to the Brewfather database. While ppgs were calculated they actually aren’t required! All that needs to be provided is the coarse grind as is extract.

Screenshot 2019-05-24 07.43.17

The ppgs line up with what was calcuated, which is a great way to validate that the new fermentable has been entered correctly.

Different Malsters. Different COAs

Every malsters COA will look different, however with armed with the knowledge above it should be possible to find the required information to determine how much sugar a new malt will contribute to a brew. Instead of substituting a specialty pilsner malt from your local micro malster as “Canadian Pilsner Malt” with a note, it can be listed in recipes as the proper malster and product.

References

  • How to Brew (4th Edition) John Palmer; Brewers Publications
  • A Handbook of Basic Brewing Calculations; Stephen Holle; MBAA

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About Chris

If there is a place that serves or sells beer I've never heard of, I'll find a way to get there. A fan of the humble Pale Ale, though always willing to try a pint of something new. I also enjoy brewing my own beers and love sharing the science of the beer making process.