Journal of Food, Agriculture and Environment

Sorption isotherms of albumen dried in a spout fluidised bed

Author(s):

Divair Christ ¹*, Rosiane Lopes da Cunha ², Florencia Cecilia Menegalli ², Katiuchia Pereira Takeuchi ³, Silvia Renata Machado Coelho ¹, Lúcia Helena Pereira Nóbrega ¹

Recieved Date: 2012-01-16, Accepted Date: 2012-04-30

Abstract:

Dehydrated products are characterized by low water activity and a low volume when compared to the original weight, for easy handling, storage and transportation. A study of the sorption isotherms provides the information necessary to fit the drying and packaging parameters. Thus, this trial aimed to collect sorption isotherm data for albumen dried in a spout fluidised bed, correlated by several classical mathematical models. Samples of albumen containing 3.1% moisture on a dry weight basis (d.b.), underwent adsorption at 5, 10, 15, 25, 40 and 70°C in environments with controlled water activity, ranging from 0.1 to 0.93, until reaching the equilibrium moisture content, and the experimental data was applied to the Sigma-Copace, Sabbah, Oswin, modified Henderson, modified Halsey, Copace and Smith models. It was concluded that the equations matched the experimental data well for the ranges of temperature and relative humidity studied. The Sigma-Copace model was the one that best represented the hygroscopicity of the product, with a magnitude of adjustment of 0.95, mean relative deviation of 22.98 and root mean square error of 2.41. The isosteric heat of sorption was evaluated by means of the Classius-Clapeyron equation. The Vivanco-Pezantes equation best described the behaviour of the net isosteric heat, which increased due to the lower water availability of the product. This equation presented a magnitude of adjustment of 0.98 and mean relative deviation of 4.53. The Vivanco-Pezantes model predicted the values for the isosteric heat of the albumen powder more accurately than the traditional models, and indicated that below 20% d.b., the water became more tightly bound, requiring larger amounts of energy to dry the egg white. 

Keywords:

Egg white, equilibrium moisture content, mathematical modelling, isosteric heat

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 2
Category: Food and Health
Pages: 151-155

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