Critical Electric Field Strengths of Onion Tissues Treated by Pulsed Electric Fields
Article first published online: 22 SEP 2010
© 2010 Institute of Food Technologists®
Journal of Food Science
Volume 75, Issue 7, pages E433–E443, September 2010
How to Cite
Asavasanti, S., Ersus, S., Ristenpart, W., Stroeve, P. and Barrett, D. M. (2010), Critical Electric Field Strengths of Onion Tissues Treated by Pulsed Electric Fields. Journal of Food Science, 75: E433–E443. doi: 10.1111/j.1750-3841.2010.01768.x
- Issue published online: 22 SEP 2010
- Article first published online: 22 SEP 2010
- MS 20090980 Submitted 10/02/2009, Accepted 03/26/2010.
- critical electrical field strength;
- electrical properties;
- pulsed electric fields;
- pyruvate formation;
- tissue integrity
Abstract: The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (Ec) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-μs pulses indicate that breakdown of the plasma membrane occurs above Ec= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either Ec= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.