Falling number, or Hagberg falling number, is the time in seconds a plunger takes to fall through a heated paste of flour or ground grain and water, measuring alpha-amylase activity.
In trade practice
Rain at harvest starts germination, enzyme activity rises and the number falls; such flour gives sticky crumb in bread. Very high values mean little enzyme, which bakers correct with malt flour. ISO 3093 is the reference method.
In a specification
State a minimum, and for bread flour a maximum, with ISO 3093 and the moisture basis named.