Use of the rubber elasticity theory to characterize the viscoelastic properties of wheat flour doughs

The viscoelastic properties of durum wheat flour doughs were measured using the extensigraph in uniaxial extension and the Rheometrics mechanical spec trometer in oscillatory shear. The research examined the effect of increasi ng density of cross-links on rubber elasticity in these systems. The stress -strain behavior of durum wheat flour dough was not well simulated by Moone y-Rivlin type nonlinear elasticity. Addition of increasing amounts of iodat e made the dough show appreciable strain thickening behavior, approximating the behavior of natural rubbers The estimated apparent molecular weight be tween cross-links ranged from 10,500 to 16,000, much larger than that of ru bbers, for which values are in the range of 500-1,000. When the Mooney-Rivl in equation was tested, it appeared to approximate only moderately well the extensional behavior of iodate-added wheat flour doughs at finite but low extensions, where the finite extensibility of chains is not a factor. It is hypothesized that the crosslinked network is highly diluted with hydrogen and hydrophobic bonds that limit the applicability of rubberlike elasticity theories. Increasing the cross-linked density using iodic acid developed m atrices that moved the behavior of durum flour doughs closer to Mooney-Rivl in behavior.