INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY ISSN Print: 1560–8530; ISSN Online: 1814–9596 07-160/GVR/2008/10–1–112–119 http://www.fspublishers.org Review Article To cite this paper: Mirsaeedghazi, H., Z. Emam-Djomeh and S.M.A. Mousavi, 2008. Rheometric measurement of dough rheological characteristics and Rheometric Measurement of Dough Rheological Characteristics and Factors Affecting It HOSSEIN MIRSAEEDGHAZI, ZAHRA EMAM-DJOMEH 1 AND SAYED MOHAMMAD ALI MOUSAVI Department of Food Science and Engineering, Faculty of Biosystem Engineering, College of Agriculture, University of Tehran, Karaj, Iran 1 Corresponding author's e-mail: emamj@ut.ac.ir ABSTRACT Bread is one of the most important foods consumed all over the world. This review focuses on the use of rheometer for the measurement of dough rheological properties and factors affecting them. Rheological properties of dough are very important in bread baking quality. Knowledge of the rheological behavior of bread dough is very important to understand mechanical properties of the dough and control finished products. Small amplitude oscillatory shear (SAOS) measurements afford the measurement of dynamic rheological functions, without altering the internal network structure of materials tested and are far more reliable than steady shear measurement. Viscoelasticity of dough is related to many factors such as nature of flour, dough ingredient, temperature, water uptake, air incorporation and type of mixing. There are many models to predicate dough rheology. In this work some of these models such as power low, linear Maxwell model, Lethersich's model, Peleg’s model and etc., were presented. The instruments such as farinograph, mixograph, Rheomixer, Extensigraph, Alveograph, Amylograph, Maturograph, Oven Rise Recorder, Fermentometer, Dynamic oscillatory, Concentric cylinders, Parallel plates, which are used for the measurement of dough rheological properties (due to viscoelastic behavior of dough) were also described. Key Word: Bread; Dough; Rheology; Flour; Rheology models INTRODUCTION Rheology is now well established as the science of the deformation and flow of matter. It is the study of the manner in which materials respond to applied stress or strain. All materials have rheological properties. These properties are described by rheometers. Many rheometers are used for the measurement of the dough rheological properties such as penetrometer, consistometer, amylograph, farinograph, mixograph, extensigraph and alveograph described later. Bread dough is a viscoelastic and shear thinning material combined of Hookean solid and non-Newtonian viscous liquid. Dough has non-linear rheological behavior, but in very low strains has linear behavior. The amount of low strain in which dough has linear behavior, depends on the type of dough, mixing and testing method. Storage modulus (G') and loss modulus (G") can describe materials rheological properties described as follow: 0 0 cos γ θ τ = ′ G factors affecting It. Int. J. Agri. Biol., 10: 112–119 0 0 sin γ θ τ = ′ ′ G The storage modulus can be used as a measure of the lastic component of the sample and similarly, the loss odulus- the viscous component of the sample. When strain is below 0.1%, G' is greater than G", but hen e m w greater strain is used, this ratio becomes reversed due to viscoelastic solid conversion to elastoviscous liquid (Rasper, 1993). Addition of some ingredient such as yeast and salt to water-flour mix causes thixotropic behavior. Viscoelastic behavior of dough is attributed to gluten protein (Shiau & Yeh, 2001). Greater amounts of protein in water- starch-gluten system causes greater G' and lower G" (Rouillé et al., 2005). Dough having a high protein quality has a greater G' and lower tg į than a weak one (Khatkar et al., 1995; Toufeili et al., 1999). Gluten has viscoelastic behavior in which gliadin fraction represents viscous behavior and glutenin fraction represents elastic behavior due to difference in molecular size of these fractions (Tsiami et al., 1997; Spies, 1997; Edwards et al., 2001). Hydrophobic reactions have key role in elastic behavior of dough (Launay, 1990). Glutenin has a major role in the difference between baking processes (Toufeili et al., 1999). When gliadin to glutenin ratio increases elasticity decreases considerable as G' decreased due to gliadin plasticising effect and interference of gliadin with glutenin-glutenin interactions and tg į increased (Khatkar et al., 1995). Increase of protein in dough causes larger consistency. Increasing intermolecular cross-linkage causes higher G' G G tg ′ ′ ′ = δ and lower loss tangent in dough. The interactions (including physical & chemical forces) among protein molecules play key roles on the rheological properties (Shiau & Yeh, 2001). With increasing gliadin/glutenin ratio