Modification denotes the chemical breakdown of compounds that reside naturally in grain. The process is also known as enzymatic conversion, degradation, or solution. See enzymes. For brewers, the key substances in grain are starches and proteins. See proteins and starch. In their natural state, starches and protein molecules are much too complex to be suitable for beer making. Starches are carbohydrates that occur in the form of long chains or branched tree-like cluster formations. Carbohydrates can have wide variations in complexity, from highly complex structures such as cellulose (wood), to starches proper, to less complex structures called sugars. Proteins are nitrogen-based compounds. They, too, come in large- and small-molecular form. The degree of modification, then, is the degree to which starches are converted to malt sugars; and long protein chains are split up into smaller ones, including into yeast nutrients called amino acids.
A common method of measuring modification in base malt is the Middle European Analyzing Commission for Brewing Technologies/European Brewery Convention (MEBAK/EBC) Calcofluor-Carlsberg method. This analysis relies on the progressive breakdown of beta glucan-rich endosperm cells as a correlated marker for modification. See endosperm and glucans. It involves taking kernel samples from a base malt batch after kilning. The sample kernels are then cut longitudinally in half and stained with a fluorochrome solution (calcofluor), which binds with beta glucans and a green dye (called Fast Green FCF) to mask nonspecific fluorescence. When the stained kernels are inspected under ultraviolet light, the unmodified cells appear fluorescent bright blue, whereas the modified cells appear a dull blue. Each kernel in the sample is then assessed as to its percentage content of modified cells. Next, the kernels are counted in six categories of increasing modification percentages (0% to 5%; 5% to 25%; 25% to 50%; 50% to 75%; and 75% to 100%). These data are then used to compute an aggregate modification index, expressed as a percentage value, for the entire batch from which the sample was taken. The brewer will look for a modification level that suits the beer being made and the brewing technique employed. Single-temperature infusion mashes tend to require malts with high modification percentages, but brewers employing temperature-programmed mashes can use less modified malts and those using decoction can use malts that other brewers would find undermodified. See mashing. Note that the MEBAK/EBC test is not intended for such specialty malts as Munich, caramel, or crystal.
Friability is another, albeit indirect indication of malt modification, which is the capacity of malt to be crumbled or crushed during milling. See friability. Like modification, it is expressed as a percentage value and indicates the extent of the grain’s mealiness (as opposed to hard “glassiness”). Insufficiently modified malt will be relatively less mealy than properly modified malt. An acceptable base malt should be at least 75% friable; 80% is considered good, whereas 88% is considered excellent. Friability values above 95%, on the other hand, could be an indication of structural defects of the endosperm, often caused by pest infestations.
See also dextrins, diastase, fructose, glucose, maltodextrins, maltose, maltotriose, melibiose, proteolysis, sucrose, and sugar.