研究概要

Sorption isotherms and thermodynamic of water sorption of Capsosiphon fulvescens prepared by hot-air and freeze drying

研究機関名

Daegu University, Korea

http://foodsys.daegu.ac.kr/leejun

代表者

Dr. Jun Ho Lee (Professor in Food Engineering)

本研究の要旨

  The moisture sorption isotherms of hot-air dried and freeze dried Capsosiphon fulvescens powders were obtained using gravimetric static method at 25, 35, and 45℃ over a water activity (aw) range of 0.112-0.936, respectively, which showed type III behavior with a temperature inversion effect at aw above 0.8. Eight different mathematic models, Brunauer-Emmett-Teller (BET), Gugghenheim–Anderson–de Boer (GAB), Oswin, Modified Oswin, Halsey, Peleg, Henderson and Kuhn equations, were selected to fit the experimental data. The parameters of these models were determined by using nonlinear regression analysis, and the goodness of fit was evaluated by using statistical tests such as R2, P% and MSE. The BET model was found to be the most suitable model to describe the relationship between equilibrium moisture content and water activities (aw< 0.45). The Clausius-Clapeyron equation was used to determine the net isosteric heat, which decreased with moisture contents. The net isosteric heat of moisture adsorption in hot-air dried Capsosiphon fulvescens powder varied from 9.39 to 13.19 kJ/mol within the moisture content range of 0.055-0.090 (dry basis, kg H2O/kg solid); while the net isosteric heat in freeze dried Capsosiphon fulvescens powder varied from 9.75 to 30.66 kJ/mol within the same moisture content range. A linear relationship exists between the differential enthalpy and entropy.

Moisture adsorption isotherm for Caposiphon fulvescens at selected temperature

Fig.1 Moisture adsorption isotherm for Caposiphon fulvescens at selected temperature (●25 ºC, ○35 ºC and ▼45ºC, — corresponding Peleg model, – – Halsey mode).

Effect of moisture content on the net isosteric heat of adsorption values of Capsosiphon fulvescens

Fig.2 Effect of moisture content on the net isosteric heat of adsorption values of Capsosiphon fulvescens

Differential enthalpy and entropy relationship for adsorption in <I>Capsosiphon fulvescens</I> by hot air drying and freeze drying

Fig.3 Differential enthalpy and entropy relationship for adsorption in Capsosiphon fulvescens by hot air drying and freeze drying

Coefficients of determination for GAB model at different temperature

Table.1 Coefficients of determination for GAB model at different temperature



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