Water vapor sorption determination of starch based porous packaging materials
2000
Tsiapouris, A. | Linke, L.
Starch-based packaging materials of different compositions were manufactured in a thermopressing solidification process. These porous materials were used for investigations on their water vapor sorption behavior. The adsorption isotherms at 20 degrees C and the water vapor adsorption during storage of samples in conditioned air with a relative humidity of 93 % at 23 degrees C were determined. The sigmoidal type isotherms obtained were modeled using the BET (Brunauer-Emmett-Teller) and GAB (Guggenheim-Anderson-de Boer) equations and linear regression analysis. The GAB model showed a good fit to experimental data for water activities of up to about 0.9. A prediction of water vapor adsorption in dependence ontemperature up to 50 degrees C was obtained with good accuracy by using the GAB equation. It was shown that the two methods of describing the water vapor sorption behavior of starch-based products correlate with each other. In order to obtain quick results about the sorption behavior of materials for practical applications, the method of determination of moisture uptake between two relative humidities is suggested. Furthermore, it is possible to simulate the whole sorption isotherm of a starch-based product with the help of the GAB equation by determining the mass of dry matter and the water vapor adsorption between 50 % and 93 % RH only.
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