About this book
Cereal chemists are interested in rheology because the dough undergoes some type of deformation in every phase of the conversion of flour into baked products. During mixing, dough is subjected to extreme deformations, many that exceed the rupture limit; during fermentation, the deformations are much smaller and therefore exhibit a different set of rheological properties; during sheeting and molding, deformations are at an intermediate level; and, finally, during proofing and baking, the dough is subjected to a range of deformations at varying temperatures. Accordingly, the application of rheological concepts to explain the behavior of dough seems a natural requirement of research on the interrelationships among flour constituents, added ingredients, process parameters, and the required characteristics of the final baked product. At any moment in the baking process, the rheological behavior, that is, the nature of the deformation, exhibited by a specific dough derives from the applied stress and how long the stress is maintained. The resulting deformation may be simple, such as pure viscous flow or elastic deformation, and therefore easy to define precisely. Moreover, under some conditions of stress and time (i. e. , shear rate), doughs behave as ideal materials and their behavior follows theory derived from fundamental concepts. Under usual conditions encountered in baking, however, the rheological behavior is far from ideal; shear rates vary widely and sample size and dimensions are ill-defined.
cereals food processing process engineering processing rheology transport