The latest TA.XTplus
texture analyser has the option of continuously variable speed, which
allows tests to be performed at constant strain rates and higher
temperatures more relevant to proof and baking conditions. In
the traditional Dough
Inflation System
method, bubble inflation tests were limited to a fixed rate of
inflation, and both strain and strain rate varied during the test.
Because dough is viscoelastic, its rheological properties vary with
both strain and strain rate. Therefore it is necessary to
separate out the effects of strain and strain rate by keeping one
constant whilst varying the other. In the new dough inflation test
strain is varied and measures as the bubble inflates, and by
continuously changing the speed at which the bubble is inflated,
strain rate is kept constant.
Work at Reading University as part
of a MAFF funded LINK project has shown that the stability of failure
in single dough bubble walls is related directly to the extensional
strain hardening properties of the dough, and that strain hardening
plays an important role in the stabilisation of bubble walls during
baking. Strain hardening measured at 50°C and constant strain
rate for a number of commercial flours of varing quality using the
new TA.XTplus has been related to commercial breadmaking performance.
