Comparative evaluation of the effects of pulsed electric field and freezing on cell membrane permeabilisation and mass transfer during dehydration of red bell peppers

• Published in: Innovative food science & emerging technologies 2003-06, Vol.4 (2), p.177-188
• Main Authors: Ade-Omowaye, B.I.O., Taiwo, K.A, Eshtiaghi, N.M., Angersbach, A., Knorr, D.
• Format: Article
• Language: English
• Subjects: Diffusion rate; Drying; Freezing; High intensity electric field; Pulse numbers; Quality
• ISSN: 1466-8564; 1878-5522
• DOI: 10.1016/S1466-8564(03)00020-1

The extent of cell membrane permeabilisation due to high intensity electric field pulses (HELP) varying number of pulses (1–50) using electric field of 2 kV/cm, 400 μs pulse duration and freezing on mass transfer and vitamin C content during osmotic (50° Brix sucrose at 40 °C) and convective air (60 °C, 1 m/s for 5 h) dehydration of red bell peppers was studied. Total pore area due to HELP increased with number of pulses while freezing resulted in total pore area of almost 6 times as greater as the highest value from the HELP process. Higher water loss was observed for all HELP treated than for prefrozen samples while slow freezing provided samples with the highest solids uptake. The correlation coefficient ( R 2) of linear regression between water loss and solids gain estimated from either total solids or soluble solids measurement ranged from 0.954 to 0.998 suggesting the possibility of using the soluble solids method in evaluating mass transfer kinetics during osmotic dehydration process. Drying rate during convective air-drying was more enhanced by HELP than by freezing. Electrical conductivity of the osmotic solution increased with the degree of permeabilisation to a given medium value after which no further increase in the release of the intracellular ions was observed. Minimal vitamin C depletion was observed immediately after HELP treatment. The order of magnitude of vitamin C retention was untreated>frozen>HELP pretreated samples with 1 pulse>5 pulses>50 pulses>10 pulses>20 pulses after osmotic dehydration. The reduction in vitamin C content of HELP treated samples after convective drying ranged from approximately 11 to 24% while freezing resulted in approximately 24% decrease compared to the untreated samples.