SELECTION OF CHEMICAL AND THERMAL PRETREATMENT COMBINATION TO REDUCE THE DEHYDRATION TIME OF SOUR CHERRY (Prunus cerasus L.)

Sour cherry (Prunus cerasus L.) is a good source of anthocyanins showing antioxidant and anti‐inflammatory activities. Contemporary drying processes of fruits and vegetables should be fast and at relatively low drying temperatures to minimize the energy consumption and the thermal degradation of their nutritional composition. Therefore, sour cherries placed into sample bags were dipped in one of eight different pretreatment combinations consisting of chemical solutions (2% ethyl oleate, 2% K₂CO₃, 1% citric acid or water) and dipping temperature (23 or 60C) for 1 min to accelerate the skin moisture diffusivity by breaking down the waxy cuticular surface of sour cherry. Pretreated sour cherry samples were dehydrated by three different methods (artificial drying, solar drying and open sun drying). Sour cherries treated with 2% ethyl oleate solution at room temperature (23C) were the fastest to reach the final weight loss percentage (75%). They dried in 24 h in the laboratory tray dryer providing 45.2C drying air. The untreated samples reached the same weight loss percentage of 75% at a drying time of 92 h. A high dipping temperature (60C) eliminated the positive effect of ethyl oleate. Solar drying and open sun drying of sour cherries treated with 2% ethyl oleate at room temperature finished approximately in 149 h and 372 h, respectively. The color of dried sour cherries was used as a quality indicator. The increase of dehydration time decreased redness values as seen in solar drying and open sun drying. The recommended pretreatment and drying processes for sour cherries are dipping them into 2% ethyl oleate solution at room temperature for 1 min and then drying them artificially at 45.2C air temperature to effectively retain their original color.