Understanding Malt COAs
You can brew tasty, even award-winning, beer without ever needing to read a malt lot analysis, aka Certificate of Analysis (COA). Most homebrewers and small craft breweries rely on the generic analysis already embedded in brewing software or average gravity points per gallon or liter. But barley, like all seasonal crops, changes from year-to-year, region-to-region, and crop-to-crop. Small changes in seasonal and regional malt quality affect how the mash behaves, including, but not limited to, mash efficiency. For large breweries where even a tiny change in mash efficiency can equal hundreds of thousands of dollars in extract loss, small improvements can lead to huge gains. For the small brewer, it may appear as just a blip that is chalked up to process deficiencies.
But there are other reasons to read, or at least understand, the COA. All malts are not created equal. Some malts, such as six-row, have a higher protein percentage and diastatic power than standard two-row, while others, such as dextrin malts, may or may not have diastatic power of their own. Some malts can be particularly gummy; others may even require a protein rest. This information (and much more!) can be found on the malt COA.
You will find loads of information on a COA that won’t make any sense without at least a casual understanding of all the acronyms, numbers, and percentages. To complicate matters, malt COAs are not standardized from maltster to maltster. Some maltsters include information others leave off, or the information’s acronym is written slightly differently from brand to brand. In addition, European COAs use different acronyms and measuring units than American COAs. Still, every COA should contain information regarding the malt’s color, moisture, protein content, extract potential, and, if applicable, diastatic power.
The example in Figure 1 is a rundown of what one might encounter on a typical 2-row pale malt COA. It’s intended to give the brewer enough information to get a basic idea of what is encountered on a COA and what information may need to be input into a recipe formulation spreadsheet or software. For example, the “ideal range” will not be typical of higher-kilned or specialty malts but will give the brewer an idea of whether the malt is suitable for a single infusion (or not) or if any special handling is required. Following is a more detailed but brief explanation of each COA data point.
Color
In North America, malt color is measured in either Lovibond (°L) or Standard Reference Method (SRM), and in Europe, it is measured in European Brewery Convention (EBC). Often, both North American and European measurements are included on the COA.
Lovibond and Standard Reference Method are close enough to be considered the same for base malts, but the differences become larger as malt color passes about 10 ºL/12.8 SRM. To convert SRM to Lovibond, add 0.76 to SRM and divide by 1.3546; to convert SRM to EBC, multiply SRM by 1.97. Calculators are also available online that easily translate between Lovibond, SMR, and EBC.
Brewing malts range from 1.6 SRM/3.2 EBC to 850 SRM/1675 EBC. The higher the number, the darker the malt. Higher-kilned base malts, such as Munich malts, will have a higher color than paler base malts and a more pronounced “malty” flavor. Higher kilning temperatures also tend to denature enzymes, so the darker the malt, the less diastatic power it usually has. Highly kilned malts, such as roasted and crystal malts, will have no viable diastatic power.
Moisture Content
All malt contains some moisture after kilning, but too much can cause storage problems; plus, brewers don’t like paying malt prices for water. A typical range for moisture content is 3–5% and, in some cases, as high as 6%. Malt with higher than 6% moisture content may have shelf-life problems caused by mold or insects.
When malt is fully analyzed to provide the COA, moisture is one of the analyses. The moisture content of malt is determined by weighing a sample, completely drying in a drying oven, determining the dry weight, and then calculating the moisture content of the original sample. Extract is reported in dry-basis and as-is, or with moisture, terms. Brewers use as-is extract for routine brewing calculations because malt contains moisture, and use dry-basis when comparing extract differences from different malts.
Extract Potential
The extract potential tells the brewer what to expect from the wort’s specific gravity (SG) based on their mash efficiency and the available enzymes. Laboratory mashing is much more intensive than what is typically used these days in most breweries, and lab extract numbers are almost always higher than what is produced in the brewery. Although the lab results differ from brewing results, lab extract potential gives the brewer an understanding of what the malt can produce and what the brewer can expect.
Malt labs run malt samples through the basic extract test using finely ground and coarsely ground malt samples. The results from these tests are known as Fine Grind (as-is), or FG-AI, and Coarse Grind (as-is), or CG-AI, where the “as-is” designation means that the extract potential has been determined using a given weight of malt that includes the moisture. Once the malt lab has determined moisture, FG-AI, and CG-AI, then FG-DB (Fine Grind-Dry Basis) and CG-DB (Coarse Grind-Dry Basis) is calculated.
Extract potential varies by malt variety, protein level, fertilizer application, irrigation/rainfall, and other environmental conditions. These days, most brewing malts produced around the world range from 78–84% FG-DB extract.
FG/CG Difference
The difference between the FG-DB and CG-DB tests gives insight into how well the malt is modified. A high FG/CG percentage will indicate that the base malt is not yielding its extract as easily. Any difference above 1.5% means a protein rest and step mash may be beneficial. Below this percentage, the malt is suitable for a single-infusion mash.
Determining Extract Potential/PPG using the COA
Points per Pound per Gallon (PPG) are based on the assumption that one pound of malt mashed and sparged in one gallon of water would yield 1.035 SG at 100% efficiency. Our mash efficiency is then calculated as a percentage of this number (for example, at 75% mash efficiency, we could estimate 1.026 PPG).
This is still a functional method used to calculate an average recipe, getting us close enough for homebrew using the average base malt. But if we want to be more specific, we can use the CG-DB and FG/CG Difference found in a malt COA to determine the malt’s extract potential. We also need to know the moisture content since, for the CG-DB test, all the malt’s moisture is removed, and our malt will have moisture content.
The easiest way to determine the PPG is first to use a known factor that always gives us the exact same starting gravity every time it is dissolved in a measured quantity of water: Sucrose. One pound (0.45 kg) of sucrose or refined table sugar dissolved in one gallon (3.8 L) of water will always give 1.046 SG. Using this known quantity, we can determine the extract potential of any malt based on its COA.
Using our sample malt COA from Figure 1, we see that the CG-DB = 79% while our FG/CG Difference = 1%. The moisture content of our malt is 4%. Since the lab removed the malt’s moisture to perform the lab mash (called a congress mash), we must add it back to determine our FG/CG “as is” (or with moisture). To do this, subtract the moisture content percentage from the FG/CG Difference and then multiply this by the CG-DB. So: CG-DB x (FG/CG – moisture %) = FG/CG “as is”
Or: 79 x (1 – 0.04) = 75.84 FG/CG “as is”)
This means our malt has an extract potential of 75.84. However, we must still convert it to PPG (Points per Pound per Gallon) using the known PPG of sucrose (1.046).
So: PPG sucrose x FG/CG “as is” = malt PPG (@100% efficiency)
Or: 46 x 0.7584 = 34.8 PPG (or 1.035 @ 100% efficiency)
Since we will never get 100% efficiency on our mash, we determine our actual PPG by multiplying the outcome by our mash efficiency. If our efficiency usually is 75%, then:
35 x 0.75 = 26.25 or 1.026 PPG (at 75% efficiency)
Knowing how to determine the malt’s extract potential helps to understand if sudden lulls in efficiency are due to process flaws or if it is the malt itself. It also lets the brewer understand what to expect if using an unusual malt. With the variety of craft maltsters that have popped up, understanding extract potential is a powerful tool.
Diastatic Power (DP)
A malt’s ability to convert starches into sugars is quantified by its Diastatic Power (DP), which measures alpha and beta amylase. This is usually denoted in degrees Lintner (°L ; not to be confused with Lovibond) on the COA. The DP may also be written as Windisch-Kolbach (°WK) in Europe. These numbers can be converted from one to another: Lintner = (WK + 16) / 3.5 or as WK = 3.5 x Lintner – 16. Often, the COA will display both.
Without diastatic enzymes, we wouldn’t have beer as we know it because we need the enzymes to break the starches into sugars to make a wort digestible by brewer’s yeast. The higher the DP, the more modified the malt. For an all-grain mash to fully convert itself, the malt must be at least 35–40 °L (106–124 °WK). Malts with higher DP can convert themselves and a portion of unmalted adjuncts. The higher the DP, the higher the percentage of adjuncts that can be added. North American malts tend to have higher DP than European malts, with American 6-row malt having enough enzymes to convert a large portion of adjuncts as commonly used in American adjunct lagers. In general, lighter base malts will have more diastatic power. Higher-kilned base malts, such as Munich malts, usually have less DP.
DP measurement becomes critical when using higher-kilned base malts such as dark Munich, which may have a DP as low as 35–40 °L (106–124 °WK). Base malt with a lower DP may take longer to convert or have a lower mash efficiency. Therefore, when using large percentages of malt with a lower DP, adding some Pilsner or even six-row malt is sometimes beneficial, giving the mash a bump of extra enzymes.
Protein
Protein makes up a large percentage of malt. It’s imperative to have some protein for basic mouthfeel, body and head retention, and basic yeast nutrients. However, too much protein in malt can cause problems such as permanent haze and inconsistent color.
When using adjuncts with low or absent protein content, such as corn or rice, it’s important to use a malt with sufficiently high protein and enzyme content to make up for the adjunct deficiencies. Because of barley breeding efforts to meet the needs of large, global breweries, most North American and European 2-row malts can easily handle up to about 25% dilution from adjuncts without any problem. Although 6-row varieties are still grown, all of the large North American breweries, such as Anheuser-Busch Inbev and MolsonCoors, now almost exclusively use 2-row barley varieties.
Maltsters may list Total Nitrogen (TN) instead of Total Protein (TP). One percent Total Nitrogen equals 6.25% Total Protein. To determine the TP, multiply TN by 6.25.
Total Protein: The ideal protein percentage for base malt is between 9–12.5%. Malt with higher protein will have more enzymes but lower extract potential, while a lower protein malt will have fewer enzymes but more extract potential. In all-malt beers, protein over 12.5% can cause haze or lautering problems. Conversely, under 9% and head retention, mouthfeel, and body may suffer.
Sometimes, a brewer may want to use a portion of malt with a higher protein percentage, such as a specialty malt (like six-row, dextrin, wheat, or chit malt), to increase mouthfeel and head retention. This may be especially true if using adjuncts low in protein, such as sugar, corn, or rice.
Soluble Protein: This is the measurement of protein in soluble form and indicates how much protein can be extracted from the mash. It’s primarily used to determine the S/T measurement, described next.
S/T (Soluble Protein/Total Protein Ratio): During malt modification, proteins in the grain are broken down and become more soluble. The higher the S/T ratio, the more modified the malt. Anything over 35% can be considered highly modified. Most lightly kilned base malts should have an S/T ratio of about 40–46%. Anything lower than 35% would need a step mash with a protein rest or a decoction mash to make the protein more soluble. Anything above 50% could result in a thin, watery body and mouthfeel. To determine the S/T, divide the soluble protein by the total protein (S/T = SP / TP)
FAN (Free Amino Nitrogen): Amino acids are an essential micronutrient in malt wort. On a malt COA, FAN is the measurement of amino acids. These are low molecular-level proteins that develop in the barley during germination.
A higher-modified malt will generally have a higher FAN measurement. A measurement of 150–250 ppm is ideal. Anything below 150 ppm can cause yeast health problems. If using large amounts of unmalted adjuncts, such as corn or rice, you need to use a malt with a higher FAN measurement since adjuncts do not have the necessary FAN for yeast health. Levels of FAN above 250 ppm indicate that the malt is excessively modified and could produce a thinner beer.
Beta-Glucans
Beta-glucans directly affect wort viscosity and can cause a slow or stuck lauter. All malts have some level of beta-glucan since it is present in barley and reduced in size, but not eliminated, during malting. Some cereals, such as wheat, rye, and oats, typically have higher levels than barley. Beta-glucans are generally considered a potential problem at levels over 140 ppm.
Friability
Friability is the measurement of how easily a malt crushes. Malt that crushes easily and breaks into uniform pieces when milled is ideal. The friability of the malt should be over 80%. Anything under this is questionable because low friability is associated with under-modified malt, higher-moisture malt, and malt produced from barley with a high proportion of dead kernels. On the other hand, friability above about 90% is indicative of well-modified malt.
This is an edited excerpt from Keith T. Yager’s Unlocking Homebrew: The Four Keys to Tasty Beer (self-published, 2024). Available from Amazon at: www.amazon.com/Unlocking-Homebrew-Four-Keys-Tasty-ebook/dp/B0CT6Y2BS7