Combined effect of pulsed electric field and osmotic dehydration pretreatments on mass transfer and quality of air‐dried pumpkin

Abstract

Pulsed electric field (PEF) and osmotic dehydration (OD) pretreatment can accelerate the time-consuming drying process and minimize its high energy demands. The effect of PEF and OD pre-processing conditions and osmotic solution composition on mass transfer kinetics (water loss, solid gain, water activity) and quality properties (color, texture, total sensory quality) during OD and subsequent air-drying (AD) of pumpkin was studied. Application of PEF (2.0 kV/cm-1500 pulses) significantly enhanced mass transfer during subsequent air-drying (increased effective diffusivity coefficient D es and drying rate k drying , respectively). PEF and OD treatments led to a significant reduction of the processing time by 12 and 10%, respectively (p < 0.05). The maximum reduction of processing time by 27% (p < 0.05) (compared to untreated sample) resulted in combined use of PEF and OD as pretreatments prior to AD. When PEF pretreatment was combined with OD prior to AD, the corresponding energy was by 50% less than the respective energy required for nonprocessed samples.

The Effect of Ultrasound and Pulsed Electric Field on the Osmotic Dehydration Process of Strawberries

“…After 2 h of dehydration, the material previously treated with a PEF was characterized by a lower parameter compared to the material subjected to the osmotic dehydration process alone, while strawberries treated with ultrasound had higher ∆E values, but they were not statistically significant. Paraskevopoulou et al [60] found no significant differences in brightness (L*) between the fresh, PEF-pretreated, and osmotic dehydrated samples. Other studies have shown that a PEF can retain its color by releasing the intercellular content depending on the initial characteristics of the raw material, cell membrane permeability, and process conditions [60].…”

“…Paraskevopoulou et al [60] found no significant differences in brightness (L*) between the fresh, PEF-pretreated, and osmotic dehydrated samples. Other studies have shown that a PEF can retain its color by releasing the intercellular content depending on the initial characteristics of the raw material, cell membrane permeability, and process conditions [60]. In turn, research by Tylewicz et al [56] showed that the initial PEF treatment on the osmotic dehydrated of strawberries led to an increase in the L* value compared to the untreated strawberries.…”

“…The changes in the US-treated samples might be related to dissolution of pectin in cell walls as a consequence of ultrasound treatment, which results in reduced firmness [62]. By contrast, in case of the PEF treatment, research conduct by Paraskevopoulou et al [60] showed that 120 min of osmotic dehydration and a PEF treatment (35.1 kJ/kg) helped maintain the hardness of the pumpkin, not differing significantly from the texture of the fresh samples. However, Dermesonlouoglou et al [63] found that the firmness of osmotically dehydrated samples surpassed the corresponding values of freshly cut pumpkin samples.…”