The texture of foods, including the properties that determine how consumers bite and swallow, is an important part of developing more pleasurable foods. To fully understand these characteristics, better testing methods and devices are needed to detect the movement in liquid materials, especially foods that are complex liquids, such as jellied desserts.
Test devices were improved using different geometries in the test chamber, and more recently, better results have been obtained using information from rheological tests in conjunction with results from other tests, such as interior visualization techniques and ultrasound imaging. However, traditional methods could not provide information about time-dependent properties.
In a study published this week in Physics of Fluids Taiki Yoshida, Yuji Tasaka and Peter Fischer present an updated method that allows linear viscoelasticity and phase delay to be measured simultaneously opaque liquid. The ultrasound spinning rheometry method they have developed uses food speed profiles in the equation of motion to capture information about complex rheological properties.
The researchers used the popular Japanese dessert Fruiche, which contains pulp and whole milk and turns into a gel form with an egg-shaped structure. The complexity of this fluid includes properties that are difficult to measure with conventional rheometry methods due to the influence of shear, shear banding, shear localization, wall slip, and elastic instability.
"Assessing food rheology as a function of time is a challenging goal," Yoshida said. "Based on the equation of motion, the ultrasonic spin rheometry method can evaluate the instantaneous rheological properties from the measured velocity profiles to represent real rheological properties and their time dependence from the perspective of physics of fluids."
The updated method has applications in chemical engineering for understanding polymerisation and dispersion densities as well as in complex fluids such as clay, with applications in construction and in cosmetics. The researchers want to further develop the method to get more information about the invisible properties of complex fluids. They also plan to develop the industrial aspects of the technology, including inline rheometry for test samples flowing in a tube.
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Taiki Yoshida et al., Ultrasonic Spinning Rheometry Test to Investigate the Rheology of Gelled Foods to Produce Better-Tasting Desserts, Physics of Fluids (2019). DOI: 10.1063 / 1.5122874
Centuries-old food testing method updated to include complex fluid dynamics (2019, November 8)
retrieved on November 9, 2019
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