Observing the flow of porridge: a physical and rheological analysis

As the world’s population ages, the number of patients with trouble swallowing (known as dysphagia) is also increasing. Those patients need food requiring little chewing, so the ingredients are cut up or blended into tiny pieces for easy swallowing.

However, understanding the flowing and spreading of these foods is important for ensuring their safety when swallowed by patients, so Ohie et al. used velocity-profiling-assisted rheometry (VPAR) to study three types of porridge.

“Many fluid foods are heterogeneous fluids containing millimeter-sized particulates,” said author Kohei Ohie. “Conventional measurement tools that assume spatial homogeneity have been unable to reliably measure their viscosity.”

Observing the movement of fluids, such as the way that sauce spreads on a plate, can be a valuable tool for estimating their viscosity — which is how VPAR works.

The researchers chose to study three types of rice porridge using VPAR, since it is a nutritious staple for patients within care facilities.

“All the porridge was found to exhibit shear-thinning behavior, where viscosity decreases with an increase in shear rate, one of the properties essential for optimal swallowing foods,” Ohie said.

The high correlation between the rheological data and experimental observations of the spreading and simulated swallowing results was surprising to the researchers and validated the accuracy of physical models.

“By complementing conventional rheological measurement tools with VPAR, we would like to encourage researchers in both industry and academia to take on the challenge of exploring the rheology and fluid dynamics of complex fluids that were previously considered unattainable,” Ohie said.

Source: “Rheology of fluid foods containing millimeter-sized ingredients examined by velocity-profiling-assisted rheometry and prediction of spreading and descending behaviors,” by Kohei Ohie, Satomi Kumagai, Yuji Tasaka, and Yuichi Murai, Journal of Rheology (2025). The article can be accessed at https://doi.org/10.1122/8.0000919 .