Determination of Optimum Osmotic Dehydration As a Pretreatment in Hot Air Drying of Turnip Slices By Response Surface Methodology (RSM)

The objective of the present study was to investigate the effect of concentration of osmotic solution (30, 45 and 60%, w/w), temperature osmotic solution (30, 40 and 50°C), immersion time (4, 5 and 6 h) on water loss (WL), solids gain (SG), weight reduction (WR), vitamin C content, shrinkage, rehydration ratio (RR), and color indexes (L, a, b) during osmotic dehydration-drying of turnip slices. Response surface methodology (RSM) was also used to find out the optimum condition. The results showed that during osmotic dehydration of turnip samples, the variables of temperature of osmotic solution, solution concentration and time of immersion had significant effects on mass transfer parameters (WL, SG, and WR), vitamin C content, shrinkage, RR, and color index (L). Optimal conditions of osmotic dehydration for turnip were found to be: solution temperature of 45 °C, osmotic solution concentration of 58.29, and immersion time of 20 min. Under these conditions, the amounts of WL, SG, WR, shrinkage, rehydration ratio (RR), vitamin C content, and color indexes (L, a, b) were 83.10, 12.91 and 70.19%, 27.76, 4.19 and 11.64 (mg/100 g solids), 33.85, 25.49 and 15.91, respectively. The results of this study can be used in the minimal processing of turnips slices using osmotic dehydration and subsequent drying of samples.