Drying kinetics and physical changes of osmotically pretreated potato (Solanum tuberosum L.) slice

Potato (Solanum tuberosum L.) is world's main crops that owing poor storability characteristic in unprocessed state due to high water content. One of most widely used preservation method for vegetables such as potato is drying process with steam blanching and osmotic dehydration as pretreatment. Blanching and osmotic dehydration pretreatment are used for reducing water content as well as enhance dried product quality by immersing the product into hypertonic solution. In present study, potato slice blanched by steam for 3 min then soaked into three different type of salt as osmotic agent, i.e. NaCl, KCl and CaCl2 with different concentration (10, 15, and 20% (v/v)). The drying process was conducted using hot air dryer at 40°C for 4 h. The results indicated that higher concentration of hypertonic solution give greater water loss and solid gain value. The initial water content of pretreated potato slice was significantly decreased due to osmotic dehydration compared to non pretreated slices. The final potato slice water content with 10% KCl of pretreatment was slightly lower than other pretreatment combination. The drying rate of potato slices with 10 and 20% of CaCl were the lowest rate with almost similar pattern. Pretreatment with 10% CaCl was considered as the most effective pretreatment in terms of better surface color and minimum shrinkage of potato slice. The microscopy image showed that starch granules of potato were spread and invisible due to starch gelatinization. The appearance of cell wall was not clear with less shrinkage of potato microstructure.