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Helen S. Melito, Christopher R. Daubert, E. Allen Foegeding
Creep and large amplitude oscillatory shear behavior of whey protein isolate/.-carrageenan gels
Appl. Rheol. 22:6 (2012) 63691 (14 pages) ►

Dynamic oscillatory and creep tests are two common rheological methods used to determine viscoelastic properties. In the food industry, these tests are generally performed in the linear viscoelastic region, providing information on food structure and behavior over a range of timescales. However, this small-strain testing gives an incomplete picture of structural deformation and breakdown. Nonlinear oscillatory and creep testing, on the other hand, may yield a more complete fingerprint of food structural behavior. In this study, whey protein isolate (WPI)/k-carrageenan gels with different structures were studied under large amplitude oscillatory shear (LAOS) and creep tests to determine the impact of structure on nonlinear oscillatory and creep behavior, and to examine correlations between nonlinear oscillatory and creep parameters. Evaluated structural types comprised a homogeneous protein gel, a bicontinuous gel, in which both WPI and k-carrageenan exhibited a continuous network, and a carrageenan continuous gel. Creep data were fit to 4-element Burgers models for further analysis, and the predicted compliance values were found to be in agreement with experimental data (R² ≥ 0.90). Carrageenan continuous gels showed the greatest degree of nonlinearity under LAOS (25 % strain), while homogeneous gels displayed the least. Nonlinear oscillatory data was found to correlate (R² > 0.7, p < 0.05) with parameters used in the 4-element Burgers model. Hence, nonlinear viscoelastic behavior among materials may be evaluated by both creep data and nonlinear oscillatory data. However, nonlinear oscillatory data gives a quantitative measure of the type and extent of nonlinear behavior, while creep data indicates only the presence of nonlinear behavior. By combining information on structural behavior derived from nonlinear oscillatory and creep data, it is possible to determine nonlinear behavior over a wide range of timescales, yielding insight into structural deformation and breakdown under application of stress or strain at different rates.

► Cite this publication as follows:
Melito HS, Daubert CR, Foegeding EA: Creep and large amplitude oscillatory shear behavior of whey protein isolate/.-carrageenan gels, Appl. Rheol. 22 (2012) 63691.

Deepti Tanjore and Christopher R. Daubert
A vane-in-cup approach to measure viscoelastic properties of gelatin gels through torque-time responses from Brookfield YR-I viscometer
Appl. Rheol. 21:6 (2011) 63172 (11 pages) ►

Viscoelastic properties are traditionally measured using sophisticated instrumentation, and the high cost of these rheometers may limit utility. This research attempts to enable viscometers that can provide a torque-time response, with vane attachment and a recommended cup size, to measure viscoelastic properties. Phase angles and shear moduli of model systems (gelatin and polyacrylamide gels) were calculated using torque-time response and deformation zone concept. The methods were applied to data obtained from Brookfield YR-I viscometer and the calculated values were compared with the data obtained from oscillatory testing on a stress controlled rheometer. The methods were improved in several areas by testing different cup sizes, rotational speeds, and viscometers and correcting torque-time responses to obtain most accurate results possible. The developed method, along with the torque-time response obtained from the viscometer, was capable of measuring viscoelastic parameters for the tested materials and further development could design a new quality control device directed towards viscoelastic property measurement.

► Cite this publication as follows:
Tanjore D, Daubert CR: A vane-in-cup approach to measure viscoelastic properties of gelatin gels through torque-time responses from Brookfield YR-I viscometer, Appl. Rheol. 21 (2011) 63172.

J.J.Resch, C.R.Daubert
A Recap of Rheological Analysis of Foods: Theory and Practice
Appl. Rheol. 10:3 (2000) 146-147 ►

► Cite this publication as follows:
Resch JJ, Daubert CR: A Recap of Rheological Analysis of Foods: Theory and Practice, Appl. Rheol. 10 (2000) 146.

T. A. Glenn III, K.M. Keener, C.R. Daubert
A Mixer Viscometry Approach to Use Vane Tools as Steady Shear Rheological Attachments
Appl. Rheol. 10:2 (2000) 80-89 ►

► Cite this publication as follows:
GlennIII TA, Keener KM, Daubert CR: A Mixer Viscometry Approach to Use Vane Tools as Steady Shear Rheological Attachments, Appl. Rheol. 10 (2000) 80.

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