The falling number (FN), also referred to as the Hagberg number or Hagberg–Perten number, is the internationally standardized (ICC 107/1, ISO 3093-2004, AACC 56-81B) and most popular method for determining sprout damage. With the falling number test, so-called weather- or sprout-damaged wheat or rye, which adversely affects bread-making quality, could be detected at the grain silo intake within a few minutes.
Sprouting, or pre-harvest germination, is caused by damp or rainy weather conditions during the final stage of maturation of the crop. The germination causes an accelerated production of the starch-degrading enzyme alpha-amylase. Severely sprouted grain kernels can contain several thousand times the amount of enzyme of sound un-sprouted kernels. Because of this, very low levels of severely sprouted kernels mixed into sound wheat can cause the entire lot to exhibit significant amylase activity. Since its introduction in the early 1960s, the FN test has become a world standard in the grain and flour milling industries for measuring alpha-amylase activity in wheat, durum wheat, triticale, rye and barley, as well as milled products made from these grains.