In general, modification refers to the extent to which the endosperm breaks down. During the malting process, enzymes break down the cell structure of the endosperm, releasing nutrients necessary for yeast growth and making the starch available for enzyme degradation during mashing. Modification of the endosperm correlates with growth of the acrospire. As the acrospire grows, chemical changes are triggered that result in the production of numerous enzymes, which are organic catalysts. Their function is to break down the complex starches and proteins of the grain.
Degree of Modification
One traditional measure of modification is the length of the acrospire. Generally, the growth of the seedling is allowed to progress until the acrospire is just over three-fourths of the length of the grain. At this point, the acrospire is considered fully modified. Longer or shorter or longer acrospire lengths are referred to as “over” and “under” modified malts, respectively.
American versus Continental Malts
Generally, American malts are more modified than continental malts but not as modified as those produced in England or Ireland. American six-row malted barley has as much higher nitrogen content than traditional lager malt, and its enzyme strength is correspondingly greater. Therefore, high kiln temperatures can be held longer for American malts than with continental malts without risking a serious depletion of the malt’s enzyme strength.
Click on the following topics for more information on barley malts.