Sorption Isotherms of Pears Using Different Models

Abstract

In the present work the desorption isotherms of 2 cultivars of pears produced in Portugal were determined for the temperatures of 20, 30 and 40°C. This range of temperatures was selected because it covers the range of average daily temperatures in Portugal in the summer, when the solar drying of pears takes place. The data were obtained using an orthogonal distance regression algorithm (ODR) to five different models found in literature, namely Chen, Guggenheim-Anderson-de Boer (GAB), Halsey, Henderson, and Oswin. From the present work, it was possible to conclude that the 2 cultivars of pears studied show a similar behavior, and that at constant moisture content an increase in temperature enhances water activity. By comparing the different models, it was possible to conclude that the Oswin model is less appropriate for describing the drying process, and that neither the Chen nor the Halsey model is adequate. The Henderson, and particularly, the GAB models were very good at describing the different situations.