Moisture adsorption properties and adsorption isosteric heat of dehydrated slices of Pastirma (Turkish dry meat product)

Moisture sorption characteristics of dehydrated pastirma were investigated at 15 °C, 20 °C and 30 °C over a water activity (aw) range of 0.2–0.9. Sigmoidal (type-II) adsorption isotherms were observed for pastirma. The experimental sorption data obtained were applied to the Halsey, Harkins-Jura, Smith, BET, Henderson, Freundlich and GAB isotherm equations to test fitness of these equations to pastirma. The order of the best fit of sorption data obtained for pastirma at 15 °C, 20 °C and 30 °C in all the range of aw studied (0.2–0.9) was Harkins-Jura > Halsey > BET > Smith > Freundlich > GAB > Henderson, respectively. In the range aw 0.2–0.55, BET model has a better fit than in the range aw 0.2–0.9. Isosteric heats of adsorption were evaluated by applying the Clausius–Clapeyron equation to experimental isotherms and decreased with increasing moisture content.