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Characterization of postharvest changes in onion and their relation with storage time

Castellone, Vincenzo LU (2016) KLT920 20142
Food Technology and Nutrition (M.Sc.)
Abstract
Onion (Allium cepa L.) is the most economically important Allium crop. The commercial cycle of onion starts with the harvest and expect for the bulbs a conservation in bulks or in storage area at controlled temperature and relative humidity. The storage period need a particular attention because coincides with the dormancy period, when plants stop their growth, so it is very important to prolong the storage potential as much as possible. The most important moment in onions cultivation is the moment when the dormancy start. Dormancy is a period where the biological activities of bulbs are reduced. This period starts when the climatic condition become unfavorable for the life of the bulbs, and is exactly when this period starts begin that... (More)
Onion (Allium cepa L.) is the most economically important Allium crop. The commercial cycle of onion starts with the harvest and expect for the bulbs a conservation in bulks or in storage area at controlled temperature and relative humidity. The storage period need a particular attention because coincides with the dormancy period, when plants stop their growth, so it is very important to prolong the storage potential as much as possible. The most important moment in onions cultivation is the moment when the dormancy start. Dormancy is a period where the biological activities of bulbs are reduced. This period starts when the climatic condition become unfavorable for the life of the bulbs, and is exactly when this period starts begin that the onions are harvested, because the consumption of energy and oxygen is low. Deterioration in store is largely due to resumption of growth. The long term aim of this project at Lund University in collaboration with Swedish Agricultural University is to find a compound that can be used as marker to determine the storage time of the onions. The objective of this MSc thesis was to develop methods and analysis to characterize onions during storage. An onion consists of different layers and they all differ from the outer shell to the center, so to monitor the ongoing biological activities in the onions during storage the three segments: outer layer, middle layer and the inner layer are studied. The results show that water activity show no correlation between samples according to harvest time. The results show some differences between growing fields, but there are similarities between the values of the bulbs from fields A and B, A and C and between C and D fields, the data show no significant differences in water activity trough the layers. The total soluble contents analysis indicates that there are not significant differences in onion according to the harvest time, while there any similarities in onion soluble content according to the analyzed layer, so it’s possible to say that each layer has different sugars content. As of the field effect is possible to say that there are similarities between field A,B and D, but those fields are significantly different from field C. The texture analysis shows that the hardness decrease from the outer to medium layers and from medium to inner layers, the growing field and the harvest time are not relevant in modifying the texture, there are also no significant difference between growing fields and harvest time. The dry matter results suggest a greatly dependence from the harvest time, and in lesser extent from the growing field. The fructan assay results shows that the most influent factors in this assay are the growing fields and the onion layer. An histochemical analysis was made to research difference in starch. This results of this study shows that the quality parameter are mostly dependent the growing field this suggest a correlation between the quality of the crop and the culture methods. Not very influent proved to be instead the harvest time, showing that the onion can keep for a long period of time the quality parameters in an acceptable range. (Less)
Popular Abstract
This study have the purpose of investigate the internal changes in stored onion and attempt a correlation with the storage time.
Storage time is very important for industries because is during this time that the onion have the highest loss in terms of weight, nutritional substances and water and this results in an economic loss. This study focuses on finding an index or a compound that can predict the time that onions can stay stored before sprouting. The onions were stored during a phase called dormancy. In the dormancy phase onions are sleepy, so consumption of energy and respiration are at their lowest value. At the end of dormancy the onion has a life resumption and respiration rate as metabolic index start to grow and a new sprout... (More)
This study have the purpose of investigate the internal changes in stored onion and attempt a correlation with the storage time.
Storage time is very important for industries because is during this time that the onion have the highest loss in terms of weight, nutritional substances and water and this results in an economic loss. This study focuses on finding an index or a compound that can predict the time that onions can stay stored before sprouting. The onions were stored during a phase called dormancy. In the dormancy phase onions are sleepy, so consumption of energy and respiration are at their lowest value. At the end of dormancy the onion has a life resumption and respiration rate as metabolic index start to grow and a new sprout begin to come out from the neck.
In my master degree thesis were analyzed onions from 4 different growing fields (A, B, C and D), 3 different storage time (4, 11 master and 17 weeks), each onion were divided in 3 layers (outer, middle and inner layer).
The results obtained in my thesis shows: the differences in the composition of onion in the different layers, specifically the soluble solids contents (sugars, acids…) have no correlations with the storage time. Water activity analysis show an increment during storage time and this increments can be used to predict the time for storage before onions start to sprout. The results of texture analysis shows no correlation between hardness of the samples and the storage time. The dry matter content in the bulbs have shown a correlation with the storage time, decreasing during the weeks of storage. During this experimentation also the content in fructane. Fructane is composed by a long chain of fructose molecules, fructose is the sugar more present in fruit, as the name suggest, the results of fructane investigation says that can be important to analyze this compound because is positive related with hormones that can regulated the growth and life cycle of the bulbs, anyway no correlations were shown between storage time and fructane content. Essentially is possible from the results of my thesis to conclude that dry matter, activity water are correlated with the storage time. A special attention need to be put on fructane because it is not correlated to the available storage time, but is correlated with abscisic acid, an hormones that can regulate the growth of the bulbs, so can be really important to use this value to understand in which vital phase the bulbs are. About the samples that I have analyzed, from the results is possible to speculate that the decrease of fructane concentration and dry matter in the bulbs and the subsequent increment of total soluble solids can be an indicator of the end of dormancy phase. This study can be useful as a start point for more studies aimed to deepening the general knowledge about process and molecules involved in: growth, resumption of life and sprouting of vegetables and more specifically of onions. (Less)
Please use this url to cite or link to this publication:
author
Castellone, Vincenzo LU
supervisor
organization
course
KLT920 20142
year
type
H2 - Master's Degree (Two Years)
subject
keywords
post-harvest, onion, sprouting, livsmedelsteknik, food engineering
language
English
id
8564431
date added to LUP
2016-02-01 16:47:34
date last changed
2016-02-01 16:47:34
@misc{8564431,
  abstract     = {Onion (Allium cepa L.) is the most economically important Allium crop. The commercial cycle of onion starts with the harvest and expect for the bulbs a conservation in bulks or in storage area at controlled temperature and relative humidity. The storage period need a particular attention because coincides with the dormancy period, when plants stop their growth, so it is very important to prolong the storage potential as much as possible. The most important moment in onions cultivation is the moment when the dormancy start. Dormancy is a period where the biological activities of bulbs are reduced. This period starts when the climatic condition become unfavorable for the life of the bulbs, and is exactly when this period starts begin that the onions are harvested, because the consumption of energy and oxygen is low. Deterioration in store is largely due to resumption of growth. The long term aim of this project at Lund University in collaboration with Swedish Agricultural University is to find a compound that can be used as marker to determine the storage time of the onions. The objective of this MSc thesis was to develop methods and analysis to characterize onions during storage. An onion consists of different layers and they all differ from the outer shell to the center, so to monitor the ongoing biological activities in the onions during storage the three segments: outer layer, middle layer and the inner layer are studied. The results show that water activity show no correlation between samples according to harvest time. The results show some differences between growing fields, but there are similarities between the values of the bulbs from fields A and B, A and C and between C and D fields, the data show no significant differences in water activity trough the layers. The total soluble contents analysis indicates that there are not significant differences in onion according to the harvest time, while there any similarities in onion soluble content according to the analyzed layer, so it’s possible to say that each layer has different sugars content. As of the field effect is possible to say that there are similarities between field A,B and D, but those fields are significantly different from field C. The texture analysis shows that the hardness decrease from the outer to medium layers and from medium to inner layers, the growing field and the harvest time are not relevant in modifying the texture, there are also no significant difference between growing fields and harvest time. The dry matter results suggest a greatly dependence from the harvest time, and in lesser extent from the growing field. The fructan assay results shows that the most influent factors in this assay are the growing fields and the onion layer. An histochemical analysis was made to research difference in starch. This results of this study shows that the quality parameter are mostly dependent the growing field this suggest a correlation between the quality of the crop and the culture methods. Not very influent proved to be instead the harvest time, showing that the onion can keep for a long period of time the quality parameters in an acceptable range.},
  author       = {Castellone, Vincenzo},
  keyword      = {post-harvest,onion,sprouting,livsmedelsteknik,food engineering},
  language     = {eng},
  note         = {Student Paper},
  title        = {Characterization of postharvest changes in onion and their relation with storage time},
  year         = {2016},
}