Microstructure formation and rheological behaviour of dough under simple shear flow |
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| Institution: | 1. Food Science and Technology Group, Faculty of Agriculture, University of Tabriz, Tabriz 51664, Islamic Republic of Iran;2. Food and Bioprocess Engineering Group, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands;3. Wageningen Center for Food Sciences, WCFS, Diedenweg 20, 6703 GW Wageningen, The Netherlands;4. Centre for Protein Technology-TNO, WUR, P.O. Box 8129, 6700 EV Wageningen, The Netherlands;1. Soft Matter, Rheology and Technology, Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200F, Box 2424, BE 3001 Leuven, Belgium;2. Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems, KU Leuven, Kasteelpark Arenberg 22, Box 2463, BE 3001 Leuven, Belgium;3. Polymer Technology, Department of Mechanical Engineering, TU Eindhoven, Box 513, 5600 MB Eindhoven, The Netherlands;1. CSIRO Food and Nutrition, 671 Sneydes Road, Werribee, VIC 3030, Australia;2. School of Applied Sciences, RMIT University, VIC 3001, Australia;3. Faculty of Agriculture, Pattimura University, Ambon 97233, Indonesia;4. ARC Industrial Transformation Training Centre for Functional Foods, Charles Sturt University, Wagga Wagga, NSW, Australia;5. AgResearch Ltd., Grasslands Research Centre, Tennent Drive, Palmerston North 4442, New Zealand;1. College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi''an, Shaanxi 710119, China;2. School of Food and Biological Engineering, Jiangsu University, Zhenjiang, Jiangsu, 212013, China;1. CSIRO Agriculture and Food, 671 Sneydes Road, Werribee, VIC 3030, Australia;2. CSIRO Agriculture and Food, Clunies Ross Street, Black Mountain, Canberra, ACT 2601, Australia;3. AgResearch Ltd., Grasslands Research Centre, Tennent Drive, Palmerston North 4442, New Zealand;4. SP Food and Bioscience, Frans Perssonsväg 6, PO Box 5401, 402 29 Gothenburg, Sweden |
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| Abstract: | In a z-blade mixer, both shear and extensional deformations contribute to the development of dough structure. I effect of simple shearing versus z-blade mixing at similar levels of work input, on the microstructure and uniaxial extensional properties of two doughs prepared from flours of different strengths. With respect to microstructure, mixing initially increased the formation of coarse protein patches, leading to a heterogeneous dough structure with a high fracture stress (σmax) and significant strain hardening. These parameters decreased with prolonged mixing. This was accompanied by loss of glutenin macro polymer (GMP) wet weight and formation of a more homogenous microstructure. Prolonged mixing typically led to an over-mixed state. In contrast, prolonged simple shearing did not affect GMP content or strain hardening and gave enhanced shear banding. Confocal scanning laser microscopy revealed that short-term simple shearing induced structure formation in the direction of the shear flow for both flour types, followed by formation of shear-banded gluten structures both parallel and perpendicular to the direction of shear flow. Uniaxial extension of dough oriented parallel or perpendicular to the shear field did not reveal anisotropy. Apparently, the observed heterogeneity on a scale of ‘mm’ was not relevant for this type of rheology. Nevertheless, a relative weakening of dough strength (reduced fracture stress) was observed as a function of long-term shearing. This seems to be related to a local segregation effect caused by differences in visco-elasticity between the gluten phase and the starch granules. The results of this study reveal important features of the dough processing and underline the importance of not only work input, but also the type of deformation applied. |
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