Malt COA Descriptions
Here we offer brief descriptions of the various measures you might find on a malt certificate of analysis (COA). Many of the measures also have links that will take you to a deeper description the instrumentation and methods for how they are measured.
If you are feeling comfortable with this information and want to take a deeper look - consider looking at the COA from a maltsters perspective -- this will bring you further into the biology of malting. The malster uses the COA to evaluate their process and what the quality of their product is.
|Total Protein||Malt protein is the progenitor of many important qualities such as enzyme activity, color production, yeast nutrients, flavor and foam retention. The controlling factor for malt protein is the protein contained in the barley as a starting material, which is related to growing conditions (fertilization, moisture, environment) as well as variety.|
|Plumps on 6/64 screen||Measure of kernel width. Impacts mill settings. Influenced by 2 row/6 row and crop year. Typically plumper kernels have more starch and more potential for high extract.|
Definition of Friability: the condition of being friable, describes the tendency of a solid substance to be break into smaller pieces under duress. ie, the malts crushability.
A general indication of malt modification, influenced by malt process, variety and protein. Correlated w/ b-glucan and F/C difference. This measure can also be an indication of how the malt will mill.
|Moisture||Ideal malt moisture is in the range of 4-6%. Moistures outside of this range can cause milling issues. Excess moisture increases shipping costs, reduces brewhouse yield, and there is risk of mold/infection above 6%. Deficient moisture can result in shattering of husks and excessive dust during milling. Malt moisure is Influenced by kilning process and storage.|
"Fine Grind dry basis"
Total soluble content of the malt which dissolves during mashing to produce wort - primarily a measure of the amount of carbohydrates recovered from malt during mashing. It is a function of grain modification and enzyme activity and general indicator of brewhouse yield and overall performance. Over or under modification reduces extract, however different types of malt may call for varying levels of modification to create different characterstics and potential for flavor.
Some COAs may report as many as five variations of the extract measure: FGDB, FG as is, CGDB, CG as is, and F-D Difference. Fine Grind Dry Basis (FGDB) is the value most commonly reported -- think of it as the maximum potential extract a malt can have. Coarse grind and as is variations of the measure better represent what a brewer will experience. Learn more about the difference extract measures here.
Extract FGDB is measured on a laboratory wort produced from the malt. Three measures are used in the calculation: *Plato, moisture, and the grist to water ratio.
NTU = Nephelometric Turbidity Units
|Measure of clarity. Hazy worts may be caused by insufficient degredation of proteins, B-glucans, or dextrin (starch), and high concentrations of phenolic compounds.|
Viscocity (absolute cp)
cp = centipoise
|Viscosity is a measure of the breakdown of B-glucans (endosperm cell walls) during malting. Highly viscous worts can cause throughput problems in the brewery.|
|Beta-Blucan (mg/L)||B-glucan is the primary component of barley endosperm cell walls. The malting process works to break this down. High B-glucan contents in wort are related to poor malt modification and/or dead kernels. High B-glucan contents can cause high viscocity, slow lautering and filtration times and haze in beer. Influenced by crop year and environment. High B-glucan correlates w/ low S/T, high viscosity, turbid worts, low friability, and can be a cause of low extract.|
|Soluble Protein (%)||Soluble protein provides the basis for yeast nutrition and foam retention. Influenced by the amount of total protein and degree of modification. Usually correlated with Free Amino Nitrogen (FAN).|
|Color (SRM)||A major component of final beer color. Color is also indirectly related to flavor. Color is developed during kilning from sugar and soluble protein precursors.|
|FAN (mg/L)||Free Amino Nitrogen. Amino acids are required for yeast nutrition and proper fermentation. FAN forms during the malting process and is correlated w/ soluble protein.|
|pH||Base malts typically have a pH range of 5.8-6.0 with ale malts at the lower and lager malts at the higher end. Malt pH values can help plan for adjustment of liquor acidity for the particular lot of malt.|
DU = dextrinizing units
|One of the key enzymes in breaking starch down into fermentable sugars (cuts starch so B-amylase can work). Influenced by variety, growing conditions, malting and application of Gibberellic Acid (GA). Malts with low alpha-amylase will be slow to convert in the mash.|
|Diastatic Power||Roughly a measure of B-amylase. Important in starch and adjunct breakdown, this enzyme is key in the production of fermentable sugars. Influenced by protein, variety, and malting conditions - particularly kilning - high kiln temps (greater with high moisture) will de-nature this enzyme quickly - so color and flavor are a trade off for enzyme potential.|
In theory, this is a measure of modification: the larger the difference the poorer the modification
|S/T Protein||Direct measure of protein modification. Influenced by malting. As malting progresses, total protein is broken down (modified) into smaller more soluble proteins. This value is another indication of overall level of modification.|
The process of malting is a balancing act - malting barley is a living grain and proper malting must balance temperature, time, moisture, and airflow among other aspects to produce a high quality malt. In many cases there are tradeoffs for pushing the balance one way or another - this means that in terms of the COA having a high value in one place will mean you cannot have a high value in another or vise versa. A malt COA is always best evaluated when considering all of the aspects and seeing how they balance. By making a practice of looking at COAs regularly you will start to see the patterns and the data will get easier to interpret.
Below are a list of oppositional specs:
Low Moisture with High DP
DP is largely a measure of the b-amylase in malt. This enzyme is particularly heat sensitive, particularly at high moisture (which the grain is when first entering the maltser's kiln). So having high color and/or low moisture means that DP will be reduced.
Low Moisture with Low Color
As the malster dries the malt biochemical changes take place in the grain. Driving off moisture also drives the reactions that creat color and flavor - this makes it very difficult to achieve very low moisture malts without producing color.
High Color and Very Low Soluble Protein
High FAN and Low Soluble Protein
Low Total Protein and High Enzymes
These three items are inter-related. Total grain protein is largely dictated by barley variety and growing conditions and is the starting material for malt aspects such as soluble protein, FAN and enzymes. Generally speaking:
Total protein breaks down to --> soluble protein ---> FAN (amino acids) ----> amino acids can build enzymes
Protein is broken down into soluble protein and further into individual amino acids (FAN). Individual amino acids are building blocks from which the grain can produce enzymes. Therefore having very low protein to start means low potential for FAN and enzymes. The processes that degrade protein into these building blocks also depend on temperature and moisture - so having high soluble protein (needs higher moisture and temp) with low color (needs low moisture and low temp) is tough.
High Total Protein and High Extract
In grain there is typically a trade off -- low protein and high starch, or high protein and low starch. Starch is converted to sugar in the mashing process, which is largely what the extract value is measuring. Having high protein barley reduces the potential for extract in two ways - first the tradeoff mentioned above, but also protein in barley makes it dificult for water to progress through the grain during malting - making the process more challenging. High protein barley will be tougher to malt and will likely have more un-modified protein in the final malt - reducing extract as the remaining protein will make it difficult for water and enzymes to interact with the starch.
High Friability and High Moisture
For the same reasons that moisture impacts how a malt will mill - moisture impacts friability. Very low moisture malts will want to pulverize to a dust, while high moisture malts will crush less easily.