An investigation into the nature of wheat flour dough adhesive behaviour

Wheat flour dough adhesiveness was measured using a probe test developed previously. Six probes made of the following materials were used in adherence measurements: PMMA (polymethylmethacrylate), SS (stainless steel), PE (polyethylene), PVC (polyvinylchloride), PTFE (polytetrafluoroethylene) and PP (polypropylene). The specific energy of separation (ω, J/m2) was seen to vary with dough water content and probe material. The greatest ω was obtained with the PMMA probe, whereas the lowest one was obtained with the SS, PTFE and PP probes. This result was in accordance with the probe surface tension measurements. The amount of water was seen to have a stronger effect on adhesiveness than probe surface tension due to changes in dough rheology. Adherence measurements conducted with different probe materials and withdrawal rates showed that ω could be factorised into two terms, a constant value tentatively related to the thermodynamic work of adhesion, W0, and a viscoelastic function of rate of separation describing the energy dissipation in dough during debonding. A general model developed for pressure-sensitive adhesives (PSAs) was shown applicable to wheat flour dough adhesiveness. It was also demonstrated that the appropriate measure of dough adhesiveness was not the maximum tensile force, but the energy of separation per unit area of interface, as stated before for PSAs.