29C-23 |
Use of a Brookfield YR-1 Rheometer for characterization of viscoelastic properties |
L. M. PAPAGEORGE1, J. Zhang, J. L. Powell, and J. Gayo. (1) Department of Food Science, North Carolina State University, NCSU Box 7624, 238 Schaub Hall, Raleigh, NC 27695 The Brookfield YR-1 Rheometer is a relatively inexpensive instrument that uses vane technology to determine the yield stress of viscoelastic materials. The Brookfield torque response is based on the degree of a spring wind-up, therefore deviations from an ideal elastic response may be attributed to viscous dissipation. The ratio of energy dissipated to the energy stored by the Brookfield spring can be used to calculate a phase angle and other viscoelastic properties for the material. Such viscoelastic properties are currently determined by significantly more expensive instrumentation. The objective of this research was to determine if viscoelastic characterization of food materials could be obtained through analysis of torque response data collected from a Brookfield YR-1 Rheometer. A StressTech controlled stress rheometer was used over a frequency range of 0.001-0.01 Hz to characterize the viscoelastic properties of ketchup and mayonnaise at room temperature. A Brookfield YR-1 Rheometer was used to collect data for the same materials over a similar frequency range. By considering the energy stored and lost through the spring, a phase angle was determined. This information, coupled with the complex modulus determined from the linear region of the failure curve, was used to compute the storage and loss moduli. When compared with results obtained from a controlled stress rheometer, the Brookfield YR-1 generated similar viscoelastic properties (R2>0.95), specifically phase angle, storage and loss moduli. These results suggest that the Brookfield YR-1 Rheometer can be used for reliable collection of fundamental viscoelastic data of food materials, introducing a novel protocol for characterizing these important food properties.
Session 29C, Food Engineering: Rheology and texture
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