Sorption Isotherms of Tomato Slices and Onion Shreds

Experiments were conducted to determine the equilibrium moisture content of tomato (cv Roma) slices and white onion shreds at temperatures of 30, 40 and 50°C and relative humidities of 15–85% obtained from an air conditioning unit. The samples were placed on trays and the equilibrium moisture contents were determined once the samples attained the constant mass. The equilibrium moisture content–equilibrium relative humidity data were fitted to the modified Henderson, Chung-Pfost, modified Halsey, modified Oswin, and modified GAB models. The modified Henderson and modified Halsey models fitted well for the tomato slices and onion shreds, respectively, based on the coefficient of regression, mean relative percent error and standard error of moisture. The values of these parameters were, 0·985, 2·58 and 0·52, respectively, for the modified Henderson model for the sliced tomatoes and 0·991, 2·01 and 0·42, respectively, for the modified Halsey model for onion shreds.