Effect of Osmotic Dehydration as a Pre -Treatment on Air Fried Sweet Potato (Ipomoea batatas) Chips

Air frying is a modern frying technique that promises low oil content of fried products. However, the main limitation of air frying is that it requires a longer operating time than deep fat frying. Previous studies found that osmotic dehydration is beneficial as frying pre-treatment to improve the quality of fried products and reduce frying time, but to date, there is no study investigating its application in air frying. Therefore, this study aims to examine the effect of osmotic dehydration as pre-treatment on the quality of air-fried sweet potato chips. Sweet potatoes were cut into slices with the same thickness, and then soaked in distilled water, 5% sodium chloride solution, and 10% sodium chloride solution for one hour. The potato slices were then air fried at two temperatures: 160˚ and 180˚C for 3, 6, 9, 12, and 15 minutes. Then, moisture content, colour, texture, diameter shrinkage and thickness expansion were analysed. The moisture content of air fried chips decreased with the increasing of frying time. The osmo-dehydrated sample showed lower moisture content which could the reduce frying time from 12 mins to 9 mins at 160ºC. Osmo-dehydrated sweet potato slices produce paler chips, but the treatment preserved the red and yellow colour of the sample. Air fried sweet potatoes that were osmotically dehydrated samples shrank more in diameter than the control samples. The increased thickness of chips was caused by crust formation and the bubbles formed at the surface due to the barrier formed by the tight surface, resulting in vapour expansion inside the pores of the chips. The hardness of pre-treated chips increased significantly with decreasing moisture content. Using osmotic dehydration pre-treatment in the air frying process can yield promising results in less frying time and better retention in terms of red and yellow colour.