The sliced purple sweet potatoes will be osmotically partial dehydrated using the different concentrations of sucrose (40, 50 & 60 %), salt (0, 2 & 4 %), time (2, 4 & 6 hrs.) and fixed temperature (40ºC) and random stirring of osmotic solution for 2 min with the spatula at every 10 min. The slices will have placed in 1000 mL beakers containing the osmotic solutions and maintained in a bath with the temperature control. The mass ratio of the osmotic medium to the sample will be 10:1, to avoid the significant dilution of the medium and subsequent decrease of the driving force during the process.