Mass Transfer Kinetics of the Osmotic Dehydration of Yacon Slices with Polyols

Osmotic dehydration using different polyols was studied. Yacon slices were immersed in solutions of xylitol, maltitol, erythritol, isomalt and sorbitol. The kinetics of solid gain (SG), water loss (WL) and water activity (a(w)) were evaluated (0, 10, 30, 45, 60, 90 and 120min). The effective diffusion coefficients of water (D-effw) and solids (D-effs) were calculated with the models of Fick and Barbosa Junior et al. At the end of the process, the highest SG was obtained with erythritol solutions; the lowest with sorbitol and maltitol and intermediate values of SG were acquired in osmotic processes with solutions of isomalt and xylitol. The samples treated in sorbitol, xylitol and erythritol solutions presented the highest D-effw and were more effective at increasing WL and reducing a(w). The model of Barbosa Junior et al. presented the best fitness. The D-effw/D-effs ratio showed better results for osmotic processes involving sorbitol and xylitol. Practical ApplicationsYacon tuber is typical from Latin America. It is considered an important source of fructooligosaccharides (FOS). This class of carbohydrate is employed on the control of diseases such as obesity and diabetes, due its low glycemic index. However, yacon roots are highly perishable and techniques for conservation are required. Osmotic dehydration is a pretreatment process that provides partial water removal from a food product, with low energy consumption. Polyols are widely employed as osmotic agents due their low caloric value. The kinetics of mass transfer on osmotic process are function of process variables, sample matrix characteristics, molecular weight of osmotic agents and others. This study investigate the water loss, solid gain, effective diffusivity and water activity of the OD of yacon with five different polyols and provide information about mass transfer kinetics of osmotic processes using two different empirical models.