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Effect of pulsed electric field treatment in combination with hot-air drying on glandular trichomes of basil

Maspero, Umberto LU (2018) KLTM05 20181
Food Technology and Nutrition (M.Sc.)
Abstract
Pulsed electric field (PEF) treatment is a non-thermal process which has a wide range of beneficial effects in food processing. The application of pulsed electric field treatment relevant for this work is as pre-treatment on basil leaves before the drying process. It has been proven that PEF treatment can significantly reduce the drying time due to the electroporation of the guard cells of stomata, which causes the stomatal aperture to stay open during the drying process, allowing a faster water loss to the leaf.
This work is focused on the effect of pulsed electric field treatment and drying process on specific structures of the basil leaves called glandular trichomes, which are the main site of production and storage of basil essential... (More)
Pulsed electric field (PEF) treatment is a non-thermal process which has a wide range of beneficial effects in food processing. The application of pulsed electric field treatment relevant for this work is as pre-treatment on basil leaves before the drying process. It has been proven that PEF treatment can significantly reduce the drying time due to the electroporation of the guard cells of stomata, which causes the stomatal aperture to stay open during the drying process, allowing a faster water loss to the leaf.
This work is focused on the effect of pulsed electric field treatment and drying process on specific structures of the basil leaves called glandular trichomes, which are the main site of production and storage of basil essential oils. The ability of trichomes to withstand pulsed electric field treatment in different conditions before the drying process was tested, both in terms of structural integrity and constituents, with the aid of fluorescence microscopy and scanning electron microscopy.
A viable method to visualize trichomes and their constituents (terpenoids) with fluorescence microscopy was developed in the preliminary phase of the work.
Regarding trichomes it resulted that PEF treatment alone in all conditions tested is not responsible for changes in structure or in retention of terpenoids. Trichomes viability was assessed with propidium iodide test, the results showed that PEF treatment in all conditions tested does not cause the staining of the nuclei of the four secretory cells which constitute the trichome. Fluorescein diacetate test was conducted as a further confirmation of cell survival, but it was not possible to draw conclusion as far as trichomes are concerned, it was still possible to characterize leaf tissue cells survival.
The results of the drying process confirmed the premise of a faster drying time for PEF-treated leaves and reported that dried leaves which underwent a PEF treatment with harsher conditions had a lower value of water activity.
Trichomes which underwent PEF treatment before the drying showed better results in terms of keeping structural integrity, but the disappearing of noticeable terpenoids content was assessed for all dried samples, for both PEF treated and untreated control samples. (Less)
Popular Abstract
Basil is one of the most popular herbs in the world and it has many uses, the most common is for culinary purposes. Basil can be used as it is in its fresh form, or it can be dried to allow a longer shelf-life.
Drying of herbs is a very expensive process, because it requires a lot of energy and must be done at low temperatures, making the process long and time consuming. Furthermore, the quality of the final product is quite low and requires improvement.
There are treatments that can be performed on the fresh basil leaves before the drying process in order to make it faster and therefore to have a better final product. One of these treatments uses a technology called Pulsed Electric Field, which exploits electric fields to cause... (More)
Basil is one of the most popular herbs in the world and it has many uses, the most common is for culinary purposes. Basil can be used as it is in its fresh form, or it can be dried to allow a longer shelf-life.
Drying of herbs is a very expensive process, because it requires a lot of energy and must be done at low temperatures, making the process long and time consuming. Furthermore, the quality of the final product is quite low and requires improvement.
There are treatments that can be performed on the fresh basil leaves before the drying process in order to make it faster and therefore to have a better final product. One of these treatments uses a technology called Pulsed Electric Field, which exploits electric fields to cause harmless modifications to the basil leaf, allowing basil to dry faster.
The quality of dried basil depends on its content in essential oils, which are the substances that give basil its characteristic aroma and taste. These oils are naturally produced and stored by the basil leaf in specific structures called trichomes, located on the leaf surface.
This work has studied how trichomes are affected by the Pulsed Electric Field treatment before the drying takes place, a decrease in the number of trichomes would be correlated to a loss in terms of essential oils and therefore in a loss of quality. The results confirmed that the drying process can be improved in terms of duration and costs by pre-treating basil with Pulsed Electric Field. Furthermore, trichomes appeared to be able to withstand Pulsed Electric Field treatment in diverse conditions, giving rise to a possible enhancement of future food products which make use of dried basil. (Less)
Please use this url to cite or link to this publication:
author
Maspero, Umberto LU
supervisor
organization
course
KLTM05 20181
year
type
H2 - Master's Degree (Two Years)
subject
keywords
food engineering, livsmedelsteknik
language
English
id
8957008
date added to LUP
2018-09-12 10:51:56
date last changed
2018-09-12 10:51:56
@misc{8957008,
  abstract     = {Pulsed electric field (PEF) treatment is a non-thermal process which has a wide range of beneficial effects in food processing. The application of pulsed electric field treatment relevant for this work is as pre-treatment on basil leaves before the drying process. It has been proven that PEF treatment can significantly reduce the drying time due to the electroporation of the guard cells of stomata, which causes the stomatal aperture to stay open during the drying process, allowing a faster water loss to the leaf.
This work is focused on the effect of pulsed electric field treatment and drying process on specific structures of the basil leaves called glandular trichomes, which are the main site of production and storage of basil essential oils. The ability of trichomes to withstand pulsed electric field treatment in different conditions before the drying process was tested, both in terms of structural integrity and constituents, with the aid of fluorescence microscopy and scanning electron microscopy.
A viable method to visualize trichomes and their constituents (terpenoids) with fluorescence microscopy was developed in the preliminary phase of the work.
Regarding trichomes it resulted that PEF treatment alone in all conditions tested is not responsible for changes in structure or in retention of terpenoids. Trichomes viability was assessed with propidium iodide test, the results showed that PEF treatment in all conditions tested does not cause the staining of the nuclei of the four secretory cells which constitute the trichome. Fluorescein diacetate test was conducted as a further confirmation of cell survival, but it was not possible to draw conclusion as far as trichomes are concerned, it was still possible to characterize leaf tissue cells survival. 
The results of the drying process confirmed the premise of a faster drying time for PEF-treated leaves and reported that dried leaves which underwent a PEF treatment with harsher conditions had a lower value of water activity.
Trichomes which underwent PEF treatment before the drying showed better results in terms of keeping structural integrity, but the disappearing of noticeable terpenoids content was assessed for all dried samples, for both PEF treated and untreated control samples.},
  author       = {Maspero, Umberto},
  keyword      = {food engineering,livsmedelsteknik},
  language     = {eng},
  note         = {Student Paper},
  title        = {Effect of pulsed electric field treatment in combination with hot-air drying on glandular trichomes of basil},
  year         = {2018},
}