Cornell University Biological and Environmental Engineering

• Research Areas
• Biomedical Applications
• Food as Porous Media
• Combination Microwave Heating
• Thermal and Hygrostresses
• Computer-Aided Food Process Engineering

Thermal and Hygrostresses in Food Materials During Processing

We are looking at how processing of food causes cracks due to uneven temperature, moisture change or pressure generation. Both food and biomedical processes are of interest.

The oven rise in a bread baking process is being modeled by treating the dough as a viscoelastic material that changes shape as carbon dioxide and vapor forms inside. Temperature and moisture changes in the deforming dough are described using a multiphase porous media model. Changes in mechanical and other properties during the baking process are included using literature data.

In thermal stress work, we have looked at how biomaterials such as foods containing large amounts of water can crack when subjected to very rapid freezing as when using liquid nitrogen. A thermomechanical model was developed by combining cooling of the material that leads to ice formation and expansion with the stresses developed in the viscoelastic material. Biomaterials containing large amounts of water were shown to change their viscoelastic properties drastically as the water freezes. Fracture experiment and analysis showed that cracking could be avoided by following a two-step cooling procedure where temperatures are lowered slowly (slow freezing) in the temperature range of maximum ice formation (region of phase change). Below this temperature range, rapid cooling in liquid nitrogen did not cause cracks since the volumetric expansions outside the phase change region are much smaller.

Slide Show

Freeze Fracture

Selected Publications

• Coupled multiphase transport and deformation in porous media: Application to baking. J. Zhang and A. K. Datta. Presentation: Annual Meeting of the American Institute of Chemical Engineers, Reno, Nevada, November 4-9 (2001)
• Thermal fracture in a biomaterial during rapid freezing. X. Shi, A. K. Datta and S. Mukherjee. Journal of Thermal Stresses. 22(3):275-292. (1999).
• Thermal stresses from large volumetric expansion during freezing of biomaterials. X. Shi, A. K. Datta and Y. Mukherjee. The Journal of Biomechanical Engineering, Transactions of the American Society of Mechanical Engineers. 120:720-726. (1998)