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Pulsed Electric Field Treatment of Plant Tissue

Fincan, Mustafa LU (2003)
Abstract (Swedish)
Popular Abstract in Swedish

Elektriska pulser (PEF) är en nyligen introducerad icke-termisk livsmedelsprocess, som har en karakteristisk påverkan på cellmembranet. PEF-behandling innebär att livsmedlet utsätts för korta och upprepade pulser emellan en anod och en katod. Det huvudsakliga resultatet av denna process är en skada på cellmembranet, som leder till bildandet av antingen tillfälliga eller permanenta porer. Det intressanta med behandling av växtvävnad med elektriska pulser är att ingen värmebehandling behövs och på så sätt underlättas vissa processer såsom extraktion, torkning och osmotisk torkning. För att använda pulser i en kommersiell processning av växtvävnad krävs en bättre förståelse för de förändringar i... (More)
Popular Abstract in Swedish

Elektriska pulser (PEF) är en nyligen introducerad icke-termisk livsmedelsprocess, som har en karakteristisk påverkan på cellmembranet. PEF-behandling innebär att livsmedlet utsätts för korta och upprepade pulser emellan en anod och en katod. Det huvudsakliga resultatet av denna process är en skada på cellmembranet, som leder till bildandet av antingen tillfälliga eller permanenta porer. Det intressanta med behandling av växtvävnad med elektriska pulser är att ingen värmebehandling behövs och på så sätt underlättas vissa processer såsom extraktion, torkning och osmotisk torkning. För att använda pulser i en kommersiell processning av växtvävnad krävs en bättre förståelse för de förändringar i strukturen hos växtvävnad på cellnivå orsakat av dessa pulser. Efter att porer i cellmembranet bildats, sker ett antal förändringar inuti vävnaderna. Den viktigaste av dessa är förlust av turgor och påföljande spridning av intracellulärt innehåll ut ur cellen. Detta reflekteras i att de mekaniska och elektriska egenskaperna förändras i vävnaden.



I denna undersökning har utvecklats en metod som möjliggör studier av PEF-permeabilisering på cellnivå. Vi har demonstrerat att permeabilisering av växtvävnad börjar ske vid en enda puls av 100 μs vid 0.35 kV/cm fältstyrka. Tidsskalan för diffusion av intracellulärt innehåll ut i extracellulärt området är 2 min. Vid stress relaxationsstudier undersökte vi förändringar i de mekaniska egenskaperna hos växtvävnad, som var utsatta för pulser med eller utan osmotisk förbehandling. Vi kom fram till att den initiala styvheten påverkades lite medan kvarvarande elasticitet var den parameter som påverkades mest, även vid lägre nivå av pulsbehandling. Maximal pulsbehandling hade en likadan effekt som 0.7 M hyperosmotisk lösning, vilket innebär att inverkan av pulser på relaxationsbeteende kan förklaras som förlust av turgor. Varken hypoosmotisk eller hyperosmotisk förbehandling visade sig förbättra inverkan av pulsbehandling. När effekten av elektriska pulser på extraktion av färg från rödbetor undersöktes, visade det sig att en pulsbehandlingsnivå vid 1 kV/cm`s fältstyrka ledde till 90 % utbyte av ett rödbetsfärgämne vid efterföljande vattenextraktion under 1 timme. Energiförbrukningen var 7kJ/kg. En ökning av vävnadens konduktivitet efter pulsbehandling korrelerade linjärt med en extraktionsnivå upp till 60-70 %. Genom att använda bimodal Fick’s diffusionsmodell undersökte vi också extraktionshastigheten av rödbetsfärgämnet och några salter. Processen visade sig var styrd av en långsam och en snabb diffusionskoefficient, vilka var oberoende av behandlingsnivån. Men extraktionsandelen som skedde med den högre hastigheten, ökade med behandlingsnivån. Den snabbare diffusionskoefficienten var 2-5 gånger lägre än den motsvarande diffusionskoefficienten i utspädd lösning. (Less)
Abstract
A pulsed electric field (PEF) is a newly emerged non-thermal food processing technology which has characteristic effects on the cell membrane. PEF processing involves subjecting food to short, repeated pulses of a high electric field between an anode and a cathode. The main result of this process is the disruption of the cell membrane leading to the formation of either temporary or permanent pores. The area of interest in the treatment of plant tissue with PEF is facilitation of certain processes such as extraction, drying and osmotic dehydration, non-thermally and economically. For PEF to be employed in commercial plant tissue processing, a better understanding of the changes brought about by PEF in the structure of plant tissue at the... (More)
A pulsed electric field (PEF) is a newly emerged non-thermal food processing technology which has characteristic effects on the cell membrane. PEF processing involves subjecting food to short, repeated pulses of a high electric field between an anode and a cathode. The main result of this process is the disruption of the cell membrane leading to the formation of either temporary or permanent pores. The area of interest in the treatment of plant tissue with PEF is facilitation of certain processes such as extraction, drying and osmotic dehydration, non-thermally and economically. For PEF to be employed in commercial plant tissue processing, a better understanding of the changes brought about by PEF in the structure of plant tissue at the cellar level is required. After the formation of pores in the cell membranes, a number of changes are initiated inside the tissue. Most important of these is the loss of turgor, and subsequent diffusion of intracellular content out of the cell.



In the study undertaken here, a microscale method was developed making the study of PEF- induced permeabilization possible at cell level. We demonstrated that permeabilization of plant tissue starts to occur with a single pulse of 100 μs at 0.35 kV/cm field strength. The timescale for the diffusion of intracellular content into the extracellular region is in the range of 2 min. When changes in the mechanical properties of plant tissue (potato) exposed to a PEF, with or without osmotic treatment, were studied using stress relaxation, the short-term (time) modulus was found to be little affected. The residual elasticity was the parameter most affected even at lower levels of PEF treatment. Maximal PEF treatment had a similar effect to exposure to a 0.7 M hyperosmotic solution implying that the effect of PEF on relaxation behavior can be explained by loss of turgor. Neither hypoosmotic nor hyperosmotic pretreatment appeared to enhance the effect of PEF treatment. When the effect of a PEF on extraction of red pigment from red beetroot was investigated, it was found that PEF treatment level at 1 kV/cm field strength led to the extraction of about 90 % of the total red beetroot pigment following 1 h aqueous extraction. The energy consumption was 7 kJ/kg. The increase in tissue conductivity after PEF treatment correlated linearly with the extraction yield of up to an extraction level of 60-70 %. Diffusion of red pigment and ionic species in the extraction process was also studied in terms of a bimodal Fickian diffusion model. The process appeared to be governed by a slow- and a fast apparent diffusion coefficient which were independent of the treatment level. However, the fraction of the yield associated with the faster diffusion coefficient increased with treatment intensity, and at maximum PEF treatment and in frozen/thawed tissue it accounted fully for the transport. The faster apparent diffusion coefficient was 2-5 times lower than the corresponding diffusion coefficient in dilute solution. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Knorr, Dietrich, Department of Food Biotechnology and Process Engineering, TU, Berlin, Germany
organization
publishing date
type
Thesis
publication status
published
subject
keywords
bimodal Fickian diffusion model, Food and drink technology, Livsmedelsteknik, generalized Maxwell model, onion Neutral Red, visualization, red beetroot, potato, epidermis, plant tissue, electroporation, Cell permeabilization, Pulsed electric field, PEF
pages
120 pages
publisher
Mustafa Fincan (Mustafa.Fincan@ofir.dk), or Dept of Food engineering, Lund University, or The library; UB , Lund University,
defense location
Center for Chemistry and Chemical Engineering, Room A, Lund Institute of Technology
defense date
2003-04-23 10:30
language
English
LU publication?
yes
id
a3702af5-8091-4201-9fd4-76262fb54df8 (old id 465604)
date added to LUP
2007-10-14 13:39:36
date last changed
2016-09-19 08:45:06
@phdthesis{a3702af5-8091-4201-9fd4-76262fb54df8,
  abstract     = {A pulsed electric field (PEF) is a newly emerged non-thermal food processing technology which has characteristic effects on the cell membrane. PEF processing involves subjecting food to short, repeated pulses of a high electric field between an anode and a cathode. The main result of this process is the disruption of the cell membrane leading to the formation of either temporary or permanent pores. The area of interest in the treatment of plant tissue with PEF is facilitation of certain processes such as extraction, drying and osmotic dehydration, non-thermally and economically. For PEF to be employed in commercial plant tissue processing, a better understanding of the changes brought about by PEF in the structure of plant tissue at the cellar level is required. After the formation of pores in the cell membranes, a number of changes are initiated inside the tissue. Most important of these is the loss of turgor, and subsequent diffusion of intracellular content out of the cell.<br/><br>
<br/><br>
In the study undertaken here, a microscale method was developed making the study of PEF- induced permeabilization possible at cell level. We demonstrated that permeabilization of plant tissue starts to occur with a single pulse of 100 μs at 0.35 kV/cm field strength. The timescale for the diffusion of intracellular content into the extracellular region is in the range of 2 min. When changes in the mechanical properties of plant tissue (potato) exposed to a PEF, with or without osmotic treatment, were studied using stress relaxation, the short-term (time) modulus was found to be little affected. The residual elasticity was the parameter most affected even at lower levels of PEF treatment. Maximal PEF treatment had a similar effect to exposure to a 0.7 M hyperosmotic solution implying that the effect of PEF on relaxation behavior can be explained by loss of turgor. Neither hypoosmotic nor hyperosmotic pretreatment appeared to enhance the effect of PEF treatment. When the effect of a PEF on extraction of red pigment from red beetroot was investigated, it was found that PEF treatment level at 1 kV/cm field strength led to the extraction of about 90 % of the total red beetroot pigment following 1 h aqueous extraction. The energy consumption was 7 kJ/kg. The increase in tissue conductivity after PEF treatment correlated linearly with the extraction yield of up to an extraction level of 60-70 %. Diffusion of red pigment and ionic species in the extraction process was also studied in terms of a bimodal Fickian diffusion model. The process appeared to be governed by a slow- and a fast apparent diffusion coefficient which were independent of the treatment level. However, the fraction of the yield associated with the faster diffusion coefficient increased with treatment intensity, and at maximum PEF treatment and in frozen/thawed tissue it accounted fully for the transport. The faster apparent diffusion coefficient was 2-5 times lower than the corresponding diffusion coefficient in dilute solution.},
  author       = {Fincan, Mustafa},
  keyword      = {bimodal Fickian diffusion model,Food and drink technology,Livsmedelsteknik,generalized Maxwell model,onion Neutral Red,visualization,red beetroot,potato,epidermis,plant tissue,electroporation,Cell permeabilization,Pulsed electric field,PEF},
  language     = {eng},
  pages        = {120},
  publisher    = {Mustafa Fincan (Mustafa.Fincan@ofir.dk), or Dept of Food engineering, Lund University, or The library; UB , Lund University,},
  school       = {Lund University},
  title        = {Pulsed Electric Field Treatment of Plant Tissue},
  year         = {2003},
}