Water desorption isotherms of pork liver and thermodynamic properties

Abstract

For the first time, the relationship between equilibrium moisture content and water activity is reported for the desorption process in pork liver. For that purpose, a standardized conductivity hygrometer was used at four different temperatures (0, 10, 30 and 50 °C) over a wide range of water activity (0.999–0.103). Five models frequently found in the literature (GAB, Oswin, Henderson, Hasley and Ratti) were considered for the purposes of describing the experimental desorption. The GAB model emerged as the best option (explained variance 96.6%) for the physical and mathematical description of the water desorption isotherms in pork liver. The computed isosteric heat, entropy and Gibbs energy illustrated the high water-sorbent affinity, because of a considerable availability of strong sorption sites at low moisture contents.The reported experimental desorption isotherms, and modeling results, are essentials for the optimal design of the drying process of pork liver, which is a necessary step for the further research addressing the extraction of the protein fraction from the dried product. Extraction and isolation of the protein fraction from pork liver could be considered a reasonable strategy considering the demand of protein materials and the high-environmental impact of the meat industry.