Effects of pulsed vacuum osmotic dehydration (PVOD) on drying kinetics of figs (Ficus carica L)

Abstract

Drying kinetics of non-pretreated (fresh) and pretreated Sardop (Ficus carica L.) variety figs were compared. In experiments, figs were performed as a whole (unsliced and unpeeled). Pretreatment was pulsed vacuum osmotic dehydration (PVOD). Osmotic dehydration was performed in sucrose solution at 50 degrees Brix and 50 degrees C with a solution/fruit mass ratio of 4/1. Vacuum impregnation in osmotic dehydration was applied at 130 mbar for 15 min then the osmotic treatment continued at atmospheric pressure for 165 min, therefore the total pretreatment period lasted for 180 min (15 min (130 mbar) + 165 min (P-atm)). Pretreated and non-pretreated figs were dried at 55, 65 and 75 degrees C in a convective oven. Results showed that increasing of drying temperature shortened the drying time for both non-pretreated and pretreated figs. Drying period of pre-treated figs lasted shorter than non pretreated figs, thus PVOD shortened the drying period. Non-pretreated (fresh) figs had greater shrinkage than the pretreated figs. Effective moisture diffusivity (D-eff) values of pretreated figs are greater than the non pretreated figs during the drying at all three temperatures. D-eff increased with drying temperature for both pretreated and non-pretreated figs. D-eff values of non-pretreated and pretreated figs ranged 2.75.10(-10)-5.69.10(-10) m(2)/s and 3.57.10(-10)-10.25.10(-10) m(2)/s, respectively. Activation energy (E-a) of non-pretreated and pretreated figs were obtained 34.68 (kJ/mol) and 50.27 (kJ/mol), respectively. Also, sensory evaluation of color, flavor, odor, texture and overall acceptability of the samples was made. Industrial relevance: The use of PVOD technique is relevant for food industry. So that, PVOD treatment shortened the drying period of figs. Thus, thisresult can cause the economic advantage as reducing the further costs for drying process. Additionally, results of sensory evaluation show that there was no significant difference (p> 0.05) between the pretreated and traditional dried figs except for flavor. Sensory properties of pretreated figs may be improved by changing conditions of pretreatment. (C) 2016 Elsevier Ltd. All rights reserved.