Measurement of biaxial extensional viscosity of wheat flour doughs
作者:
Hsimin Huang,
Jozef L. Kokini,
期刊:
Journal of Rheology
(AIP Available online 1993)
卷期:
Volume 37,
issue 5
页码: 879-891
ISSN:0148-6055
年代: 1993
DOI:10.1122/1.550400
出版商: The Society of Rheology
关键词: Biaxial extension;Lubricated squeeze flow;Dough rheology;VISCOSITY;WHEAT;ELONGATION;STEADY FLOW;STRESSES;PROTEINS;VISCOELASTICITY
数据来源: AIP
摘要:
The biaxial extensional viscosity of wheat flour doughs was measured using the lubricated squeeze film apparatus. Two disks of different diameters, 80 and 57.2 mm, were employed, with an extension rate (0.011 s−1) which remained approximately constant with both disks. Using polydimethylsiloxane a steady state lasted from 40 to 70 s. Obtaining steady extensional flow with wheat doughs, on the other hand, necessitated 10 to 200 s depending on the magnitude of normal stresses which ranged from 5.018 to 0.361 KPa. Doughs with different protein contents (13.2%, 16.0%, and 18.8% based on 14%MB) showed different biaxial extensional viscosities. These increased with increasing protein content. At an extensional rate of 7.3×10−5s−1the biaxial extensional viscosity approached 6η; Trouton’s ratio (ratio of ηEto η) increases with extension rate. The differences between biaxial extensional viscosities and shear viscosities become more profound when viscosities are plotted versus stresses.
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