Moisture Adsorption and Spoilage Characteristics of Pea Under Adverse Storage Conditions

190 Pages·2005·2.85 MB·English

Moisture Adsorption and Spoilage
Characteristics of Pea Under
Adverse Storage Conditions

A Thesis Submitted to the College of
Graduate Studies and Research
in Fulfillment of the Requirements
for the Degree of Master of Science
in the Department of Agricultural
and Bioresource Engineering
University of Saskatchewan
Saskatoon

By
Samira Dadgar

Samira Dadgar, May 2005. All rights reserved.
PERMISSION TO USE

In presenting this thesis in partial fulfilment of the requirements for a Postgraduate
degree from the University of Saskatchewan, I agree that the Libraries of this University
may make it freely available for inspection. I further agree that permission for copying of
this thesis in any manner, in whole or in part, for scholarly purposes may be granted by
the professor or professors who supervised my thesis work or, in their absence, by the
Head of the Department or Dean of the College in which my thesis work was done. It is
understood that any copying or publication or use of this thesis or parts thereof for
financial gain shall not be allowed without my written permission. It is also understood
that due recognition shall be given to me and to the University of Saskatchewan in any
scholarly use which may be made of any material in my thesis.
Requests for permission to copy or to make other use of material in this thesis in
whole or in part should be addressed to:

Head of the Department of Agricultural and Bioresource Engineering
57 Campus Drive
University of Saskatchewan
Saskatoon, Saskatchewan S7N 5A9

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ABSTRACT

Field pea is the most produced and exported pulse crop in Canada, and makes a major
contribution to Western Canadian agricultural diversification programs. Canada is now
the world largest exporter of pea, lentil and chickpea and is fourth in dry bean. The
demand for Canadian pulse products is steadily rising and the export market would
continue to rise with the expected increased in production. Field pea exported to countries
with tropical climates is at particular risk due to rapid loss of quality. It is therefore
important to develop practical strategies for safe storage of feed pea. Knowledge on the
moisture adsorption and spoilage characteristics of pea stored in adverse storage
conditions is important in the transportation and storage of this export commodity.
This study was initiated to examine the conditions that lead to quality losses in
storage and transport of pea. Tropical and subtropical conditions were simulated in
airtight chambers. Relative humidities (RH) of 60, 70, 80 and 90% were created by
saturated salt solutions in airtight chambers at temperatures of 10, 20 and 30°C, while the
same range of humidity was provided by dilute sulphuric acid in airtight chambers at
40°C in environmental cabinets. The four RH levels at each temperature for both whole
and feed-grade pea were tested in duplicate. The samples were observed for changes in
moisture content (MC), mold appearance and RH in specific time intervals. The amount
of produced carbon dioxide (CO ) was measured in airtight chambers during storage to
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control the condition existing in sealed airtight chambers. Also, all components of feed-
grade pea were exposed to RH of 90% and temperature of 40°C in separate airtight
chambers to find the effect of each component on mold appearance. Molds were
identified after appearance on the samples in order to pinpoint potential toxicity.

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Both feed and whole sound peas became molded after a short time of storage at high
temperatures and high RH, but those stored at 70% and below did not develop mold after
175 days at 30 and 40°C (experiment duration) and 216 days at 10 and 20°C (experiment
duration). Molds were identified mostly as species of Aspergillus and Penicillium. The
amount of CO in the airtight chambers showed almost no difference from the ambient
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CO except at high temperature and high RH when samples had gone molded.
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Moisture adsorption equations were developed based on the moisture adsorption data
in dynamic environment. Although the Page model showed to fit the data better, the
exponential model was chosen to fit the data because its parameters can be better
expressed as a function of temperature and RH of the storage environment.
The mold-free days for both feed pea and clean pea were modeled at temperatures of
10, 20, 30 and 40°C and RH of 80 and 90%.

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ACKNOWLEDGEMENTS
May all Praise be to God

I would like to express my gratitude and appreciation to the people who contributed to
the development of this thesis:

My advisor, Professor Lope Tabil, for his support, guidance and encouragement
throughout all stages of this study.

The members of my advisory committee, Dr. Oon Doo Baik and Dr. Venkatesh Meda for
their guidance and support.

Mr. Bill Crerar and Louis Roth, for helping during my experiment, and for always being
there to help out.

Dr. Robin Morrall for his assistance in identifying the fungi in this study.

The staff, faculty, and students of the Department of Agricultural and Bioresource
Engineering.

The Phytotron staff.

My husband, Mohammad, for his encouragement, support and help all during my study.

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My friend, Lily Ketabi, for her help and kindness during my study.

My mother and my father for their encouragement and support during my study.

Finally, the financial support of the Department of Agricultural and Bioresource
Engineering, Agriculture Development Fund of Saskatchewan Agriculture and Food
(SAF) and Natural Sciences and Engineering Research Council.

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DEDICATION

Dedicated to my Mother, my father,
my husband and my son, Kaveh

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TABLE OF CONTENTS

PERMISSION TO USE......................................................................................................ii
ABSTRACT.......................................................................................................................iii
ACKNOWLEDGEMENTS................................................................................................v
DEDICATION..................................................................................................................vii
TABLE OF CONTENTS.................................................................................................viii
LIST OF TABLES............................................................................................................xii
LIST OF FIGURES........................................................................................................xvii
LIST OF ABREVIATIONS............................................................................................xxi
GLOSSARY OF TERMS...............................................................................................xxii
1. INTRODUCTION..........................................................................................................1
2. LITERATURE REVIEW...............................................................................................4
3.1 Effect of Moisture and Temperature on Fungal and Insect Growth.........................4
3.2 Respiration................................................................................................................8
3.3 Types of Grain Storage.............................................................................................9
3.3.1 Controlled atmosphere storage........................................................................10
3.3.2 Refrigerated storage.........................................................................................13
3.4 Storage of Pulses.....................................................................................................14
3.4.1 Storage of chickpea..........................................................................................15
3.4.2 Storage of dry bean..........................................................................................16

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3.4.3 Storage of field pea..........................................................................................19
3.5 Summary.................................................................................................................28
3. OBJECTIVES...............................................................................................................30
4. MATERIALS AND METHODS..................................................................................32
4.1 Material...................................................................................................................32
4.2 Experimental Equipment........................................................................................35
4.2.1 Airtight chamber..............................................................................................35
4.2.2 Controlled environment cabinet.......................................................................36
4.3 Protocols and Methods............................................................................................38
4.3.1 Experimental plan for storage test in the static environment...........................40
4.3.2 Moisture adsorption of pea in dynamic environment......................................41
4.3.3 Relative humidity measurement in static environment....................................43
4.3.4 Maintenance of relative humidity inside the airtight chambers.......................44
4.3.5 Weighing of the samples in static environment...............................................46
4.3.6 Measurement of CO inside the chamber........................................................49
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4.3.7 Moisture content measurement........................................................................50
4.4 Data Analysis and Processing.................................................................................53
4.4.1 Moisture ratio determination............................................................................53
4.4.2 Statistical analysis............................................................................................54
4.4.3 Model development.........................................................................................55
5. RESULTS AND DISCUSSION...................................................................................57
5.1 Moisture Adsorption of Pea in a Dynamic Environment........................................57

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5.2 Moisture Adsorption of Pea and Components During Storage in Static
Environment..................................................................................................................63
5.3 Fungi Identification.................................................................................................73
5.4 Mold-free Days.......................................................................................................79
6. CONCLUSIONS AND RECOMMENDATIONS.......................................................90
6.1 Conclusions.............................................................................................................90
6.2 Suggestions for Future Research............................................................................92
6.3 Recommendations...................................................................................................93
LITERATURE CITED.....................................................................................................94
APPENDIX A- MOISTURE ADSORPTION DATA....................................................101
A.1 Moisture Adsorption in Dynamic Environment...................................................101
A.2 Moisture Adsorption of Clean and Feed Peas during Storage in Static
Environment................................................................................................................103
A.3 Moisture Adsorption Data of Feed Pea Components...........................................118
A.3 Moisture Ratio Graphs.........................................................................................121
APPENDIX B – CARBON DIOXIDE MEASUREMENT...........................................125
APPENDIX C- MICROBIAL TEST RESULT..............................................................129
APPENDIX D – STATISTICAL ANALYSIS...............................................................135
D.1 Sample SAS Input and Output.............................................................................135
D.1.1 Sample SAS input.........................................................................................135

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