Linear Viscoelasticity of Non-Fermented Dough: Effect of Gluten Absence

VIRGINIA LARROSA ; GABRIEL LORENZO; NOEMÍ ZARITZKY; ALICIA CALIFANO

Viscoelasticity: Theories, Types and Models

Nova Science Publishers, Inc

Año: 2011; p. 93 - 113

Gluten contains the protein fractions glutenin and gliadin. Interactions of gliadins and glutenins through covalent and non-covalent bonds to form gluten complexes result in viscoelastic dough that exhibits cohesive, elastic and viscous properties that combine the extremes of the two components. It has the ability to withstand stresses applied during mixing and to retain gas during fermentation and baking, enclosing the starch granules and fiber fragments. In recent years, gluten-free bakery products have an increase demand because of the improvement in celiac disease (CD) diagnosis. The only effective treatment for CD is strict adherence to a gluten-free diet throughout the patient?s lifetime, which, in time, results in clinical and mucosal recovery. Hydrocolloids and proteins are essential ingredients in gluten-free doughs for improving their rheological properties and final appearance. The rheological characterization of doughs provides important information for food technologists, allowing ingredient selection strategies to design, improve, and optimize the final product. Rheological studies become particularly useful when predictive relationships for rheological properties of foods can be developed based on the molecular architecture of the constituent species. This chapter focuses on the linear viscoelastic characterization of gluten-free non-fermented doughs and the effect of proteins (dry egg and ovoalbumin) and hydrocolloids (xanthan and guar gums) content. Small amplitude oscillatory data (storage modulus, G?, and loss modulus, G??) were used to obtain the relaxation spectrum that was compared to the spectrum of a traditional wheat dough. The increase in gums content produced an increase in both moduli (G? and G??) and a more elastic dough was obtained. G? was always larger than G?? in the frequency measured range and the increase of the two moduli with frequency was small. The broadened Baumgaertel-Schausberger-Winter model was successfully used to predict the mechanical relaxation spectrum from dynamic oscillatory data. Gluten-free dough exhibited similar elastic modulus to those prepared with wheat flour. However, analyzing the tan(d) vs. frequency curves, commercial wheat flour dough presented distinctively higher values, which correspond to a more viscous contribution. The gluten matrix is more easily deformed under applied stress, and it is possible to correlate this behavior with large deformation experiments in which dough formulations are submitted to extensibility tests. Using the mechanical spectrum all dynamic data could be converted into the time domain by the application of BSW model. From the relaxation curves thus obtained, it could be notice the difference in the characteristic relaxation parameters of these systems.