The first time a distiller sees a certificate of analysis (COA)—possibly attached to an initial batch of raw grain or malt—it might look like Latin or gibberish. That collection of percentages, ratios, and PPMs attached to strange identifiers such as Kolbach or beta-glucan can look as impenetrable as a secret code.
However, just as a chef ought to inspect a fresh batch of steaks for marbling and quality, distillers should cast a critical eye over the grain itself, visually, as well as over the numbers in the COA. Like any agricultural product, grain is subject to variability. Different harvests, various chemical or environmental inputs, and even variations from one field to another in the same year can lead to grain that has different properties.
As a distiller, you should understand and account for those properties when planning your mashing or cooking regimen.
The first time a distiller sees a certificate of analysis (COA)—possibly attached to an initial batch of raw grain or malt—it might look like Latin or gibberish. That collection of percentages, ratios, and PPMs attached to strange identifiers such as Kolbach or beta-glucan can look as impenetrable as a secret code.
However, just as a chef ought to inspect a fresh batch of steaks for marbling and quality, distillers should cast a critical eye over the grain itself, visually, as well as over the numbers in the COA. Like any agricultural product, grain is subject to variability. Different harvests, various chemical or environmental inputs, and even variations from one field to another in the same year can lead to grain that has different properties.
As a distiller, you should understand and account for those properties when planning your mashing or cooking regimen.
[PAYWALL]
Some Key Stats to Know
One of the first things to look for is any sign of fungal issues. The most common is fusarium, a group of filamentous fungi that can cause fusarium head blight in small grains such as wheat, barley, and oats.
Fusarium infections can create a measurable amount of deoxynivalenol (DON), also known by the colorful name vomitoxin. According to FDA requirements, DON levels must be less that one part per million (ppm) in the grain, which will be noted in the COA. By inspecting the grain visually, you should be able to identify less common infections, such as ergot on rye, as well as cross-contamination with other grains or debris from the field.
Most of the crucial fields on a COA for raw grain can also be found on one for malt. Moisture content should be in the 10 to 12 percent range for raw grains and 4 to 5 percent for malted barley. Lower values are less common but acceptable, although they can indicate lower enzyme content in malted grain. Higher values can encourage staling or microbial growth in storage.
When you look at the composition of grain, the largest element by far is starch—expressed on a COA as extract. Extract is an indicator of starch, whose long-chain glucose polymers are waiting to be converted into simple sugars and fermented—so, it corresponds roughly with yield. Expressed as a percentage, extract measurement may be listed as based on fine grind, coarse grind, or both.
Extract values should be in the upper 70s to lower 80s for both fine and coarse grind. Some COAs will also include the fine/coarse difference (or F/C difference), which should be less than 2 percent. A difference of 2 percent or above—say, 78 percent extract for coarse and 83 percent for fine grind—indicates malt that is less uniformly modified.
When considering extract and calculating expected yield, note that extract is generally given on a dry-weight basis. This means that grain with 80 percent extract on a dry-weight basis, but with 12 percent moisture, is actually offering about 70 percent extract by weight. Some COAs will also include extract on an as-is basis. (Suppliers typically prioritize the dry-weight extract because it removes moisture as a variable, providing a better batch-to-batch comparison for extract potential.)
Considerations for Malt
When it comes to malt, modification is another important factor when it comes to processing and yield. Modification refers to the degree to which the malting process has altered the grain (usually barley) to allow for easier access to the starches.
The malting process breaks down the beta-glucan matrix that the grain uses to lock up and store away those energy reserves. A more complete level of modification means that the starches are more accessible, while less modification means that some of the starches remain less accessible—but not necessarily out of reach if you’re using exogenous enzymes.
In considering the level of modification, two numbers that matter are friability and beta-glucan, which have an inverse relationship. The friability—preferably 90 percent or better—is the tendency of the particles in the malt kernel to break apart; a lower level of friability means a higher level of remaining beta-glucan. The beta-glucans—which should be less than 100 ppm—are the remnants of the cell walls that once contained the storehouses of starch polymers. A high number means the kernel is harder to physically break, indicating that the malting process broke down less of the soluble fiber.
After starch, and possibly equal with moisture, protein is the last major component of grain—usually constituting 10 to 12 percent of either malted or raw grain. A COA can reflect that protein content in a couple of ways, including percentages of total protein and total soluble protein.
Those measurements also lead to another: the ratio of soluble to total proteins, or S/T ratio, also known as the Kolbach index, expressed as a percentage. For brewers, this is a factor in body and foam creation in beer. It’s not typically a concern for on-grain distillers, but all-malt distillers running off a fermentable wort should look for an S/T ratio of least a 30 to 35 percent to avoid lautering issues. A COA might also indicate this with a measurement of viscosity, where results greater than 1.6 units can indicate potential difficulty with lautering.
Another measurement linked to protein content is free-amino nitrogen, or FAN. FAN is essential to a healthy fermentation, and malted barley usually provides plenty. In general, a mash with a small amount of malt will contain enough FAN to encourage proper fermentation. (However, fermentations that lack any grain component—such as honey, molasses, or other relatively pure sugar sources—may benefit from the addition of a FAN-containing yeast nutrient.)
The primary consideration regarding protein is its inverse relationship to extract and yield. Total protein content greater than 12 percent is often considered less than optimal because it means reduced starch and lower yield. However, a small number of distillers have moved toward embracing elevated levels of protein in the quest for greater flavor—often when using unusual or older varieties of grain that haven’t been optimized for modern farm systems. While the grain proteins themselves are too long to be flavor-active, their constituent amino acids are the source of a variety of flavors and flavor precursors that can find their way into a final spirit.
Another important stat for yield is diastatic power, a measure of enzymatic activity in malt. For all-malt mashes, the DP should be at least 100° Lintner. For mashes that rely on a small amount of malt to covert an entire mash—for example, a bourbon recipe using 10 percent malt and no exogenous enzyme—the distiller should look for malt with DP of at least 180 to 200° Lintner.
Other Properties
Unmilled malt should include a few scores under the Assortment heading. These scores indicate how many of the kernels are plump versus thin, and plumps are an indicator of good starch and extract content.
Under Assortment, the lines 7/64, 6/64, and 5/64 refer to different screen sizes in a sieve analysis. The plumps are those that won’t pass through the 7/64 and 6/64 screens; those should add up to more than 80 or 90 percent; no more than a few percent should be getting through the 5/64 screen. For distillers who use a two-roller mill, such as that often seen in malt whiskey production, poor assortment can lead to an uneven grind and poor yield.
For distillers without a mill, ordering their grain pre-crushed, there is no field on the COA to describe the crush or particle-size assortment. Without knowing the nuances of a particular distiller’s equipment, the maltster or supplier may err on the side of a coarser grind, potentially sacrificing a small amount of yield to ensure that the customer doesn’t get a stuck mash. Being able to work directly with the maltster can alleviate this because they may be able to customize their grind.
Color, often noted as a Standard Research Method (SRM) score or degrees Lovibond, is a common field noted in malted barley. It’s more important for brewers and doesn’t directly impact the distiller’s needs or concerns, but darker (higher) or lighter (lower) numbers can have subtle implications for the flavor of a finished spirit—especially in more delicate whiskeys, where grain character is allowed to shine through. While the creation of caramelized and Maillard compounds during kilning can reduce yield by small amounts, they can provide additional flavor to the final spirit.
While COAs tend to have many measurements in common, they aren’t all the same; some of the above may be missing, or you may come across others I haven’t mentioned here. Communication is key: If you have any questions about the COAs you’re receiving—or if you think you may be seeing sub-optimal or inconsistent numbers—be sure to talk to your supplier.
