Diastatic power

The diastatic power (DP), also called the "diastatic activity" or "enzymatic power", of a grain generally refers only to malts, grains which have begun to germinate; the act of germination includes the production of a number of enzymes such as amylase which convert starch into sugar; thereby, sugars can be extracted from the barley's own starches simply by soaking the grain in water at a controlled temperature: this is mashing. Other enzymes break long proteins into short ones and accomplish other important tasks.

In general, the hotter a grain is kilned, the less its diastatic activity; consequently, only lightly-colored grains can be used as base malts, with Munich malt being the darkest base malt generally available.

Diastatic activity can also be provided by diastatic malt extract or by inclusion of separately-prepared brewing enzymes.

Diastatic power for a grain is measured in degrees Lintner (°Lintner or °L, although the latter can conflict with the symbol °L for Lovibond color); or in Europe by Windisch-Kolbach units (°WK). The two measures are related by

$\{\}^circmbox\{Lintner\}\; =\; frac\{\{Totally-disputed-section\}^circmbox\{WK\}\; +\; 16\}\{3.5\}$

$\{\}^circmbox\{WK\}\; =\; left\; (3.5\; times\; \{\}^circmbox\{Lintner\}\; right\; )\; -\; 16$.

A malt with enough power to self-convert has a diastatic power near 35 °Lintner (94 °WK); the most active, so-called "hottest" malts currently available, American six-row pale barley malts, have a diastatic power of up to 160 °Lintner (544 °WK).