30F-11 |
Modeling moisture migration in multi-domain foods |
S. S. R. GEEDIPALLI and A. K. Datta. Department of Biological and Environmental Engineering, Cornell University, Room No. 175, Riley-Robb Hall, Ithaca, NY 14853 Study of moisture migration in multi-domain foods is critical, as moisture content is an important factor in determining the shelf life of a food item. Moisture loss from one part of the food to another occurs continuously until equilibrium is reached. Water migration in solid foods has mostly been analyzed using the concept that water migration is driven by the gradient of water content. The real driving force however happens to be the water activity gradient rather than the moisture content gradient. This plays a major role in determining the final moisture content in foods having multiple-domains with widely different sorption isotherms. The objective here is to study the moisture migration problem in a sandwich having a low moisture bread and a high moisture filling. The bread and the filling have different water activity isotherms. A new equilibrium moisture content (based on uniformity of water activity) is defined and the problem is solved using the gradient of difference in moisture content and equilibrium moisture as the driving force. A finite element implementation of the problem was carried out using a commercial computational fluid dynamics software package, and moisture profiles as a function of time during storage have been obtained. The results show qualitative agreement to existing experimental data and clearly demonstrate that the final moisture content of each domain of the food is different. A sensitivity analysis has been carried out to see the dependence of migration on the sorption isotherms and diffusivity values. Moisture migration across domains needs to be controlled to increase the shelf life of a food item. By modeling the moisture migration, the duration of stability of a food item in storage can be predicted.
Session 30F, Food Engineering: Transport processes and kinetics
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