work in progress
--Kaiser 20:24, 26 December 2007 (CST)
When malt is crushed not only the endosperm is crushed, but also the husks which should remain intact as much as possible since they are needed as the filter bed for lautering. Depending on the tightness of the crush, enough of the husks generally remains intact to allow for smooth lautering. Besides impeding the run-off during the lauter, overly shredded husks can also contribute to astringent flavors. During the mashing process, tannins are extracted from the husks. This tannin extraction can get over the taste threshold if the pH is to high and/or the sparge water is to hot. But husk-dust can also cause excessive tannin extraction due to the significantly increased surface area of the husk material.
To alleviate lauter problems and/or astringent off-flavors, many commercial brewers either condition their malt before crushing or crush their malt wet (wet crushing). The latter is also done to reduce the O2 intake during milling and dough-in process in a modern low O2 brewhouse.