APPLICATION OF VIBRATION TECHNIQUE FOR THE CONTROL OF SPROUTING IN YAM (Dioscorea spp.) DURING STORAGE

Early sprouting of yam tuber is a typical problem during storage resulting into weight losses, deterioration, shrinkage and reduction in quality. This study investigated the application of vibration technique to control sprouting in yam tubers during storage. A mechanical yam vibrator having adjustable frequencies and amplitudes was developed with vibrating chamber of capacity size of 670 × 570 × 180 mm3 which can contain four tubers of yam at a time. The physical properties (length, number, and weight of yam sprout, number of leaves, weight of roots, weight loss, swollen value of the middle diameter and shrinkage of the length, top and bottom diameter) of the yam tubers were determined for 140 white yam tubers. Out of 140 tubers 108 were used for the experiment and 32 as control. A full 3×3×3×2 factorial experimental design based on complete randomized block design with 54 treatments and 2 replicates were used to investigate the effect of frequency, amplitude and time of vibration on the physical properties of yam tubers and sprouts. The factors of the experimental design examined for frequency, amplitude and time of vibration were low (1 – 5 Hz, 5 mm and 5 minutes), medium (60 – 100 Hz, 10 mm and 10 minutes) and high (150 – 200 Hz, 20 mm and 15 minutes), respectively; weight of the yam tubers were of two levels: small (0.1 – 2.9 kg) and big (3.0 – 5.0 kg). The tubers were stored for ten weeks after vibration, the physical properties of the yam tubers and sprouts were monitored and records were taken every week. For yam tubers of small weight, sprout lengths 135. 34, 15.43 and 9.77 cm occurred at low, medium and high frequencies respectively, while the length of the sprout on the control was 319.16 cm; similar trend was observed for amplitude and time of vibration. For yam tubers of big weight, sprout lengths 121.41, 10.51 and 6.81 cm occurred at low, medium and high frequencies respectively, while the length of the sprout on the control was 324.25 cm; similar for amplitude and time of vibration. All the physical properties of yam tubersand sprouts examined followed the same trend. It was discovered that as the frequency, amplitude and time of vibration were increasing, the physical properties of yam tubers and sprouts studied were decreasing significantly (p < 0.05) for both weight of yams 0.1 – 2.9 kg and 3.0 – 5.0 kg. There was no significant difference (p > 0.05) of the weight of yam tubers between the range of 0.1 – 2.9 kg and that of 3.0 – 5.0 kg. The results revealed that mechanical vibration significantly helps in slowing down sprouting in yam tubers.

TABLE OF CONTENTS

Contents

Page

Title Page

Declaration

Certification

Abstract

Dedication

Acknowledgments

Table of Contents

List of Tables

List of Figures

List of Plates

CHAPTER ONE

1.0. INTRODUCTION

1.1 Background Information

1.2 Statement of Problem

1.3 Aim and Objectives

1.4 Justification

1.5 Significant of the Study

1.6 Scope of the Study

CHAPTER TWO

2.0. LITERATURE REVIEW

2.1 Yam

2.2 Taxonomy and Classification

2.3 Plant Characteristics of Yam

2.4 Origin and Distribution of Yam Tuber

2.5 Production of Yam Tubers

2.6 Socio – Economic Importance Of Yam

2.7 Health Benefits of Yams

2.7.1 Improvement of digestion, cancer deterrent and bowel habits

2.7.2 Excellent source of the B – complex group of vitamins

2.7.3 Low glycemic index

2.7.4 Enhancement of nutrient absorption of the body

2.7.5 Improvement of cognitive ability

2.7.6 Source of energy and antioxidant

2.7.7 Mediation of metabolic functions

2.7.8 Good source of minerals and helps in RBC production

2.7.9 Stimulation of collagen production

2.7.10 Promotion of hair growth and prevention of premature hair graying

2.7.11 Promotion of blood circulation in the scalp

2.7.12 Management of hypertension

2.7.13 Anti – cancer effect

2.8 Nutritional Values of Yam

2.9 Morphology of Intact Yam Tuber

2.10 Anatomical Structure of Dormant Yam Tubers

2.11 Anatomical Events Leading to Sprouting and the Development of the PNC

2.12 Tuber – Head as „The Organ of Renewed Vegetative Growth and as the PNC

2.13 Dormancy in Yam

2.14 Duration of Yam Tuber Dormancy

2.15 Importance of Shortening the Dormancy of Yam Tuber

2.16 Effect of Harvest Date on Duration of Dormancy

2.17 Effect of Species on Duration of Dormancy

2.18 Effect of Variety Within a Species on Duration of Dormancy

2.19 Effect of Agroecology of Origin on Duration of Dormancy

2.20 Phases of Yam Tuber Dormancy and their Potential Control Mechanism

2.20.1 Phase 1 of dormancy and control

2.20.2 Phase II of dormancy and control

2.20.3 Phase III of dormancy and control

2.21 Causes of Storage Losses of Yam

2.21.1 Respiration

2.21.2 Dehydration of yam tuber

2.21.3 Sprouting in yam

2.22 Consequences of Sprouting in Yam

2.23 Control of Dormancy by Modification of Storage Environment

2.23.1 Daylength during storage

2.23.2 Sett size

2.23.3 Temperature

2.23.4 Relative humidity

2.23.5 Soil moistures

2.23.6 Ventilation

2.23.7 Photoperiod and spectral quality

2.24 Mechanism of Dormancy

2.25 Stages of Dormancy in Yam

2.25.1 Eco – dormancy

2.25.2 Ecto or para – dormancy

2.25.3 Endo – dormancy

2.26 Methods of Traditional Storage of Yam

2.27 Physiological and Biochemical Changes during Dormancy and Sprouting

2.28 Factors Affecting the Duration of the Dormancy Period and Sprouting

2.29 Environmental Stress of Yam Tubers

2.30 Hormones Responsible for the Control of Dormancy and Sprouting in Yam

Tubers

2.30.1 Abscisic acid (ABA)

2.30.2 Gibberellins

2.30.3 Cytokinins

2.30.4 Auxins

2.30.5 Ethylene

2.31 Effect of Vibration on the Physio – Chemical, Behavioral and Activities of

Matter, Micro – Organisms, Insect and Plant

2.31.1 Effect of gamma irradiation on the control of sprouting in crops and

tubers

2.31.2 2.31.2 Effect of music on the control of sprouting in crops and tubers

2.31.3 2.31.3 Effect of ultrasound on the micro – organism, plant and macro –

Organism

2.31.4 2.31.4 Effect of plant extract on the control of sprouting in crops and tubers

2.31.5 Effect of gibbellin on the control of sprouting in crops and tubers

2.32 Mechanical Vibration

2.33 Mechanical Vibrator

2.34 Methods of Generating Mechanical Vibration

2.34.1 Unbalance mass mechanism

2.34.2 Cam and follower mechanism

2.35 Components Parts of the Mechanical Vibrator using Cam and Follower

Mechanism

2.35.1 Vibrating table

2.35.2 Helical spring

2.35.3 Frame

2.35.4 Cam

2.35.5 Follower

2.36 Instrumentation in Measuring Vibration

2.36.1 Accelerometer

2.36.2 Vibrometer

2.36.3 Displacement transducer

2.36.4 Reflective photo – transistor

2.36.5 Frequency to voltage converter

2.36.6 Non – contact tachometer

2.36.7 Seismometer

2.36.8 Fullarton tachometer

2.36.9 Frahm tachometer

2.36.10 Variable frequency drive

2.36.11 Fast fourier transform

2.37 Feature of a Typical Vibration Response

CHAPTER THREE

3.0. MATERIALS AND METHODS

3.1 Materials used for the Construction of the Rigid Yam Tuber Mechanical

Vibrating Container

3.2 Design Consideration

3.3 Design Concept and Conceptualization

3.4 Design of Machine Components

3.4.1 Design for the shaft on which the cam would be mounted on

3.4.2 Design of the cam

3.4.3 Design of the follower

3.4.4 Design of the frame of the vibrator

3.4.5 Design of the vibrating chamber

3.4.6 Design of the helical spring

3.4.7 Selection of the Speed of Electric Motor

3.5 Selection of the Frequency of the Mechanical Yam Vibrator

3.6 Selection of the Amplitude of the Vibration Exciter

3.7 Kinematic Mechanics of the Cam and Follower Mechanism of the Yam Vibrator using Cycloid Motion at the Rise and Fall of the Follower

3.7.1 Design Specifications of the cam

3.7.2 Kinematic mechanics for the rise stage using the cycloid cam profile

3.7.3 Kinematic mechanics for the dwell stage of the cycloid cam profile

3.7.4 Kinematic mechanics for the return stage the cycloid cam profile

3.7.5 Kinematic mechanics for the dwell stage of the cycloid cam profile

3.8 Development of the Cam using Cycloid Motion

3.9 Construction of the Rigid Yam Mechanical Vibrator based on Cam and Follower Mechanism

3.10 Installation of the Yam Tuber Vibrating System

3.11 Instrumentation and Control of the Yam Tuber Mechanical Vibrator

3.12 No – Load Test on the Developed Mechanical Yam Vibrator

3.12.1 Measurement of the displacement of vibration of mechanical yam

Vibrator

3.12.2 Measurement of the velocity of vibration of mechanical yam vibrator

3.13 Evaluation of the Physical Properties of the Yam Tuber and Sprouts

3.14 Experimental Designs, Analysis and Procedures

3.14.1 The procedure in the combination of the factors to give each treatment

3.14.2 Number of treatment

3.15 Investigative Studies of the Effects of the Mechanical Vibration Interaction on the Sprouting of tthe Yam Tuber

3.15.1 Independent variables (factors) of the experimental design

3.15.2 Dependent variable (response variable) of the experimental design

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3.16 Effect of the Vibration Frequency, Amplitude and Time Duration on the Physical

Properties of Yam Sprouts

177

3.17 Evaluation and Measurement of the Yam Sprout Response

3.18 Effect of the Vibration Frequency, Amplitude and Time Duration on the Physical Properties of the Yam Tubers

3.19 Evaluation and Measurement of the Yam Tuber Response

3.20 Vibration of the Yam Tuber and Assigning of Number to the Yam Tubers

3.21 Storage of the Vibrated and Untreated Yam Tubers

Chapter Four

4.0 Results and Discussion

4.1 The Mechanical Yam Vibrator

4.2 Results of the No Load Test

4.2.1 Variation of the displacement of the vibration of the mechanical yam

Vibrator

4.2.2 Variation of the velocity of the vibration of the mechanical yam

Vibrator

4.3 Performance of the Machine on the Stored Yams

4.3.1 Effect of the machine on the physical properties of the yam sprouts

4.3.2 Effect of the machine on the physical properties of the yam tubers

Chapter Five

5.0 CONCLUSION AND RECOMMENDATION

5.1 Conclusion

5.2 Contribution To Knowledge

5.3 Recommendation

REFERENCES

APPENDIX