Diastatic malt is
malt extract that contains
enzymes called
diastase. These enzymes break starch down into simple sugars (namely
maltose) and are used as a very powerful food for
yeast in bread production. Since it contains
sugar itself and makes even more sugar available by allowing the
diastase to act on any starch present, it will increase the leavening effect of yeast more than a similar amount of plain sugar.
It also promotes browning of bread via the maillard reaction.