Comparative Study of the Thermodynamic Properties of Penaeus vannamei Shell and Meat
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Abstract:
To determine the relationships among water activity (aw), moisture content, and temperature of Penaeus vannamei shell (PV-S) and P. vannamei meat (PV), the moisture adsorption isotherms and thermodynamic properties of PV-S and PV were investigated. The moisture adsorption isotherms of PV-S and PV followed typical type Ⅱ and III behaviors, respectively. The optimum models for describing the adsorption properties of PV-S and PV were the Blahovec-Yanniotis model and GAB model, respectively. For both PV-S and PV, the net isosteric heat of adsorption (differential enthalpy) and differential entropy decreased with increasing moisture content. The spreading pressure increased with increasing aw, but decreased with increasing temperature. The integral enthalpy of PV decreased with increasing moisture content, whereas that of PV-S first increased and then decreased with increasing moisture content. The integral entropy of PV increased with increasing moisture content, whereas that of PV-S first decreased and then increased with increasing moisture content. The adsorption behaviors of PV-S and PV were enthalpy-driven and satisfied the entropy-enthalpy compensation theory. When moisture content was lower than 0.20 g/g, the net isosteric heat of adsorption and differential entropy of PV-S were higher than those of PV. The spreading pressure and integral entropy of PV were lower than those of PV-S, whereas the integral enthalpy of PV was higher than that of PV-S. At a moisture content of 0.07 g/g, the integral enthalpy and integral entropy of PV-S reached a maximum value (1.91 kJ/mol) and minimum value (–14.34 kJ/(mol K)), respectively. The results obtained in the present study will provided a scientific basis for the drying process and storage stability of dehydrated P. vannamei.
