THE RHEOLOGICAL BASIS OF DOUGH STICKINESS

Stickiness in wheat flour doughs was studied as a function of rheological and surface properties. Adhesion was measured using a modified peel test at various water additions, peel rates and peel layer thicknesses. Peeling energy gave a strong positive correlation with subjective bakery stickiness ratings. Peeling forces were highly rate dependent and showed transitions from sticky to nonsticky behvaiour with increasing rate of peeling. Dynamic storage modulus showed a negative correlation with stickiness ratings, suggesting stickiness is primarily a rheologically controlled process. Stress relaxation gradients were greater for sticky doughs and were very similar to peeling force vs. rate slopes, again indicating that adhesion is principally a function of the rheological properties of the dough. Surface tension measurements of sticky and nonsticky dough/liquor interfaces showed no significant differences and are typical of protein solutions. Calculated values of the interfacial surface energy between dough and interface were about 100 mJ/m², typical of secondary bonding interactions such as polar or van der Waals bonding.