Effects of Dipping Solutions on Air-Drying Rates of the Seedless Grapes

Abstract

Preserving of food by drying, has been became an important subject in food industry. Turkey has a high potential at fruit production. Grape has an economically important role in Turkey's export. The effects of different dipping solutions on hot air drying of grapes were studied. The Sultana grape was used ın drying experiments. Seedless grapes treated with oleic acid and potassium carbonate solutions or untreated were dried by air at 50℃, 60℃ and 70℃. Pretreated grapes dried faster than naturally dried. According to colour results, red colour on grapes pretreated with oleic acid solutions was preserved beter than naturally dried.Drying rates of grapes were modelled by the Page and Exponential equations. The model results agreed with experimental results.

Effective Maxwell−Stefan diffusion model of near ambient air drying validated with experiments on Thomson seedless grapes

“…The driving force for the drying process (which is essentially the difference between the partial pressure of water vapour in the air just above the fruit and the vapour pressure exerted by the wet surface of the fruit) can be increased in two ways. By lowering the partial pressure of water vapour in the air, which can be achieved by either dehumidifying the air or by heating the air so that the relative humidity (RH) is lowered by higher temperatures. Researchers [ 5,15,16,26–34 ] have attempted to increase the temperature difference by heating the air, in turn accelerating the drying processes. However, it should be noted that although the increased temperature results in faster drying, the efficiency of the equipment drops, due to substantial enthalpy bypassing the fruit, making it unsustainable for the industry.…”

“…Researchers [5,15,16,[26][27][28][29][30][31][32][33][34] have attempted to increase the temperature difference by heating the air, in turn accelerating the drying processes. However, it should be noted that although the increased temperature results in faster drying, the efficiency of the equipment drops, due to substantial enthalpy bypassing the fruit, making it unsustainable for the industry.…”