Water Sorption Analysis in Vegetables Using a Modified Dubinin-Astakhov Equation

Water sorption isotherms at 298 K for six kinds of fresh vegetables (carrot, daikon (Japanese radish), eggplant, potato, pumpkin and sweet-potato) were measured using a static equilibration method over saturated salt solutions in the relative humidity range from 11.3 to 97.3%. The equilibrium moisture content data were fitted to a modified Dubinin-Astakhov (DA) equation that assumes a Weibull probability density function to the desorption probability under the adsorption potential change. The modified DA equation was confirmed to be very accurate in predicting the water sorption isotherms of the vegetables. In addition, the test vegetables could be classified into two groups by the n (one of the DA parameters) values, which denote the porous degree of the adsorbent. One group consisted of carrot, eggplant and pumpkin. Daikon, potato and sweet potato belonged to the other group.