Correlation between fracture of semisweet hard biscuits and dough viscoelastic properties

Semi-sweet hard dough biscuits were considered in the present work which aims at assessing whether biscuit failure mode and dough viscoelastic properties, which depend on the resting time after mixing, can be correlated to one another. Uniaxial compressions were performed on rested biscuit doughs to determine biaxial extensional viscosities. The experimental data seemed strongly dependent on the compression rate in the 1-20 mm/min range of crosshead speed. The stress growth trend observed for doughs of different resting time showed that the extent of structural recovery increased with resting. The rheological behaviour of dough under higher extensional deformation was evaluated by means of tensile and tensile-relaxation tests, the result of which can be directly related to the sheeting extensional deformation. These data confirmed the picture of dough structural recovery. Rheological investigations were coupled with DSC determinations of the glass transition temperature, T-g. The higher T-g found for rested doughs was tentatively attributed to gluten protein polymerisation. It was finally shown that the failure mode of biscuits changes with the resting time after mixing: the longer the rest, the less the biscuit strength.