Reduction of falling number in soft white spring wheat caused by an increased proportion of spherical B-type starch granules

A low falling number (FN) in wheat indicates high alpha-amylase activity associated with poor end-use quality. We hypothesize starch - the substrate of alpha-amylase, can directly influence hot flour pasting properties and its susceptibility to alpha-amylase, which further affects viscosity. We examined the structural characteristics of starch in three soft white spring wheat cultivars grown in Idaho in 2013 (normal FN year) and 2014 (low FN year with pre-harvest rains). Our data surprisingly show that starch in some low FN wheat was not significantly degraded by alpha-amylase but had developmental changes with an increased proportion of B-type wheat starch. We reconstituted wheat starch and verified that starch with an increase of B-granules has a relatively low viscosity and high susceptibility to wheat alpha-amylase, which further facilitates the decrease of viscosity. The influence of starch structure and starch-enzyme interaction must be considered while developing a solution to the low FN issue.