Modeling of Heat of Sorption in Foods and Other Biomass Materials From Free Energy Models

Wednesday, November 10, 2010
Hall 1 (Salt Palace Convention Center)
Victor R. Vasquez, O. Hanbury and Charles J. Coronella, Chemical Engineering, University of Nevada, Reno, Reno, NV

Heat of sorption in foods and other biomass materials is very important for handling, drying, and storage. It is typically obtained via thermogravimetric analysis and the data is correlated or modeled with empirical equations. A drawback of common models used is that they usually do not provide good physical into the nature of the product and serve more the purpose of data correlation. Heat of sorption can also be estimated using equilibrium moisture data (EMC) using traditional methods based on the Clausius-Clapeyron equation. In this work, we propose a simple molecular thermodynamic model that consists on developing models for the Helmholtz free energy and using these directly to estimate the heat of sorption without using the assumptions of the Clausius-Clapeyron approach. We fin that the model gives more physical insight into the nature of the food product. Additionally, the model predictions are in very good agreement with Clausius-Clapeyron-based methods validating the fundamentals of the our approach. However, when compared with experimental measurements in many cases the predictions are systematically shifted (also the case Clasius-Clapeyron-based calculations) suggesting that the measurements might include other energetic components not included in model-based estimations of heat of sorption.

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