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Optimal Pulse Electric Field (PEF) Treatment for Drying of Carrots

Schultz Busch, Amanda LU (2018) KLTM01 20181
Food Technology and Nutrition (M.Sc.)
Abstract
Pre-treatment with pulse electric field (PEF) of whole carrots was investigated, with the aim of achieving maximal tissue damage and reduce drying time of carrot cubes. Relative electrolyte leakage (REL) measurements and trypan blue staining was used to evaluate the extent of tissue damage of carrots subjected to PEF. The investigated PEF parameters were: electric field strength, number of pulses, pulse width, conductivity of PEF medium, and total power of PEF treatment. Strength of the electric field showed to be the most influential parameter in terms of causing tissue damage in carrots. Number of pulses in the interval 35 to 300, pulse width in the interval 29 to 245 µs and conductivity of PEF medium from 291 µS/cm to 500 µS/cm did not... (More)
Pre-treatment with pulse electric field (PEF) of whole carrots was investigated, with the aim of achieving maximal tissue damage and reduce drying time of carrot cubes. Relative electrolyte leakage (REL) measurements and trypan blue staining was used to evaluate the extent of tissue damage of carrots subjected to PEF. The investigated PEF parameters were: electric field strength, number of pulses, pulse width, conductivity of PEF medium, and total power of PEF treatment. Strength of the electric field showed to be the most influential parameter in terms of causing tissue damage in carrots. Number of pulses in the interval 35 to 300, pulse width in the interval 29 to 245 µs and conductivity of PEF medium from 291 µS/cm to 500 µS/cm did not influence the extent of tissue damage in carrots when there was a constant electric field of 600 V/cm and constant total power of 3 kW. REL measurements showed around 70% of tissue damage was achieved using PEF treatments with electric field strength of 556 V/cm and above. Trypan blue staining revealed that endodermis cells of the inner cortex of the carrots were not affected by the PEF treatments. The effect of PEF as pre-treatment on drying time of carrots was compared with the pre-treatment blanching, and a combination of PEF and blanching. Due to unstable temperature in the used oven, it could not be concluded whether or not the PEF treatment reduced the drying time. (Less)
Popular Abstract
Pulse electric field creates pores in carrot cell membranes and thereby potentially reduces drying time
Some food products as for example soup mixes contain dried carrot. Drying of carrots is a long and costly process. Reducing the drying time of carrots is a way to save energy. Pulse electric field is a treatment method that can bring down the drying time of vegetables. It is a technology that uses electric charges to tear open biological cells. In this master thesis Pulse electric field treatment is applied on whole carrots. The electric field make holes in the carrot’s cell membranes. The holes will make it easier for the water inside the carrot cells to leave the carrot during drying. A sufficient strong pulse electric field... (More)
Pulse electric field creates pores in carrot cell membranes and thereby potentially reduces drying time
Some food products as for example soup mixes contain dried carrot. Drying of carrots is a long and costly process. Reducing the drying time of carrots is a way to save energy. Pulse electric field is a treatment method that can bring down the drying time of vegetables. It is a technology that uses electric charges to tear open biological cells. In this master thesis Pulse electric field treatment is applied on whole carrots. The electric field make holes in the carrot’s cell membranes. The holes will make it easier for the water inside the carrot cells to leave the carrot during drying. A sufficient strong pulse electric field treatment creates holes in the cell membrane, that even if the membrane can reseal the holes again, the carrot cells do not survive.
A Pulse electric field treatment is made up of different parameters. Some of the main parameters are: The number of pulses applied, the duration of the pulses, the frequency of the pulses, and strength of the applied electric field. In this thesis project, the influence of the different parameters on the extent of carrot tissue damaged was tested. Knowing which parameters have the most influence on tissue damage in carrot can help optimize the Pulse electric field treatment to get maximum pore creation of carrot cell membranes using the least energy. The tests showed that the applied electric field is the most dominating factor for creating pores in the cell membrane. Different cells have different limits for the electric field needed to irreversibly pierce the cell membrane. Increasing the applied electric field on the carrot results in more of the carrot cells gets killed.
Damaged carrot cells leak out electrolytes. Measuring the leakage of electrolytes from the treated carrot can reveal how much of the carrot tissue gets affected by the Pulse electric field treatment. A threshold for the electric field was found to exist somewhere between 393V/cm and 556V/cm. Increasing the electric field above 556V/cm did not result in more electrolyte leakage.
However, it turns out not all cells were affected by the Pulse electric field treatment carried out in this thesis project. A ring of cell, called the endodermis, just outside the carrot’s core managed to survive the Pulse electric field treatments. This suggest that these carrot cells have a voltage threshold for permanent pore formation in cells that lies above the highest applied electric field in this thesis (1200V/cm).
The exact reduction in drying time of carrots achieved by Pulse electric field treatment of whole carrots is still to be investigated. (Less)
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author
Schultz Busch, Amanda LU
supervisor
organization
course
KLTM01 20181
year
type
H2 - Master's Degree (Two Years)
subject
keywords
food engineering, livsmedelsteknik
language
English
id
8949564
date added to LUP
2018-06-18 14:44:45
date last changed
2018-06-18 14:44:45
@misc{8949564,
  abstract     = {Pre-treatment with pulse electric field (PEF) of whole carrots was investigated, with the aim of achieving maximal tissue damage and reduce drying time of carrot cubes. Relative electrolyte leakage (REL) measurements and trypan blue staining was used to evaluate the extent of tissue damage of carrots subjected to PEF. The investigated PEF parameters were: electric field strength, number of pulses, pulse width, conductivity of PEF medium, and total power of PEF treatment. Strength of the electric field showed to be the most influential parameter in terms of causing tissue damage in carrots. Number of pulses in the interval 35 to 300, pulse width in the interval 29 to 245 µs and conductivity of PEF medium from 291 µS/cm to 500 µS/cm did not influence the extent of tissue damage in carrots when there was a constant electric field of 600 V/cm and constant total power of 3 kW. REL measurements showed around 70% of tissue damage was achieved using PEF treatments with electric field strength of 556 V/cm and above. Trypan blue staining revealed that endodermis cells of the inner cortex of the carrots were not affected by the PEF treatments. The effect of PEF as pre-treatment on drying time of carrots was compared with the pre-treatment blanching, and a combination of PEF and blanching. Due to unstable temperature in the used oven, it could not be concluded whether or not the PEF treatment reduced the drying time.},
  author       = {Schultz Busch, Amanda},
  keyword      = {food engineering,livsmedelsteknik},
  language     = {eng},
  note         = {Student Paper},
  title        = {Optimal Pulse Electric Field (PEF) Treatment for Drying of Carrots},
  year         = {2018},
}