Moisture transport and stress development in rice during drying, a Hybrid Mixture Theory-based model

Abstract

Internal fluid flow during rice drying generates a stress gradient inside the material. If the stress gradient becomes too large or certain rice layers undergo glass transition under a significant stress gradient, stress cracks can form. In this study, modeling equations based on the Hybrid Mixture Theory were solved to simulate moisture transport and the viscoelastic stress that occurs during rice drying. The model’s accuracy was evaluated using experimental moisture content data for two rice varieties: Pusa Basmati 1121 (MAEs: 0.0079–0.0162 g/g solids) and California M206 (MAEs: 0.0022–0.0061 g/g solids). Simulations were then conducted under continuous and time-varying drying conditions to determine the best drying strategy for minimizing stress crack formation. The results showed that gradually increasing the inlet air temperature by 5 °C every 5 min after an initial 28.5 min at 40 °C could reduce stress crack formation effectively while drying rice in only 38.5 min.

Keywords:

• Drying
• rice
• stress cracking
• Hybrid Mixture Theory
• moisture transport

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgments

Thanks to ADM Institute for the Prevention of Postharvest Loss at University of Illinois, Urbana-Champaign, and USDA-NIFA for providing the financial support under award numbers ILLU-698-308 and ILLU-698-926.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

National Institute of Food and Agriculture; ADM Institute, University of Illinois.