ABSTRACT
Single-layer drying kinetics of UG I and UG II whole and split (peeled and unpeeled) treatments, for Unblanched and Blanched at 50℃ for 3, 6, and 9 minutes respectively, were investigated using solar and cabinet drying methods.There was an initial high moisture removal (constant rate period) followed by slow moisture removal in the latter stages (falling rate period) of drying.The effect of blanching on drying characteristics of UG I and UG II samples of whole peeled, whole unpeeled, split peeled, and split unpeeled treatments during solar and cabinet drying, indicates that blanching increases the drying rate. There was a significant difference between the drying curves for blanched and unblanched samples for whole and split UG I and UG II samples. This difference becomes minimum at whole peeled, split peeled, and split unpeeled treatments. This might be because, during blanching, the samples were partially cooked, and some cells or tissues of split peeled, split unpeeled, and whole peeled UG I and UG II samples might be disrupted or loosened. As a result, moisture diffusion was higher, and hence the drying rate was higher. The moisture content of the whole unpeeled UG I and UG II samples remained almost constant during the drying period, and this is true for either blanched whole unpeeled UG I and UG II samples and unblanched whole unpeeled UG I and UG II samples. This shows that the thick skin of the entire unpeeled UG I and UG II samples prevents moisture diffusion through the skin.While the drying process started with the short constant rate period, the drying bulk took place in the falling rate period. It concluded with the equilibrium moisture content threshold (EMC) being reached.The initial moisture content of 71.12% and 72.47% was reduced to the final moisture content of 6.09% and 6.94% for UG I and UG II, respectively.The drying data (MR) were fitted into ten thin-layer drying models and validated with the coefficients of determination on (R2), root means square error (RMSE), and reduced chi-square (χ2) parameters to estimate the drying behavior during the water removal stage.According to the results, the model found to explain the single layer best drying kinetics of UG I and UG II varies at different blanched treatments and unblanched compared to the other models over different experimental conditions for solar drying and cabinet drying, respectively. The results proved that the various models are efficient thin-layer models used in dryer designing and processing of UG I and UG II unblanched and blanched treatments. The data obtained were used to develop empirical equations for predicting the single-layer drying kinetics of UG I and UG II unblanched and blanched treatments for solar drying and cabinet drying methods.Proximate composition of UG I and UG II dried and milled samples with various treatments show that higher values in percentage for Unblanched UG I and UG II indicate high moisture content, ash content, crude fibre, crude protein, fat, and carbohydrate. Blanched treatment for UG I and UG II shows a reduction in percentage moisture content, ash content, crude fibre, crude protein, fat, and carbohydrate.The phytochemical analysis of UG I and UG II dried and milled samples with various treatments indicate terpenoids, flavonoids, and polyphenol. It was noted that the colour variation of flavonoids was yellow, terpenoids were brown, and that of polyphenol was blue for both UG I and UG II.
TABLE OF CONTENTS
Title page i
Certification ii
Declaration iii
Dedication iv
Acknowledgement v
Table of Contents vi
List of Tables xi
List of Figures xii
List of Plates xxi
Abstract xxii
CHAPTER ONE: INTRODUCTION
1.1 Background of Study 1
1.2 Statement of the Problem 2
1.3 Oobjectives of the Study 3
1.4 Justification of the Study 4
1.5 Scope of Study 5
CHAPTER TWO: LITERATURE REVIEW
2.1 World Ginger Production 7
2.2 Ginger Products 9
2.2.1 Fresh Ginger 9
2.2.2 Dried Ginger 9
2.2.3 Bleached Ginger 9
2.3 Ginger Quality Specifications 10
2.4 Uses of Ginger 10
2.5 Chemical And Physical Properties of Ginger 12
2.5.1 Chemical Properties of Ginger Rhizomes 13
2.6 Nutrient/Metabolic Constituents of Ginger Rhizome 15
2.7 Solar Drying 17
2.7.1 Types of Solar Dryers 18
2.8 Cabinet Drying 20
2.9 Operation Principle in Cabinet drying 20
2.10 Basic Principles In Drying 21
2.11 Drying Kinetics 23
2.12 Thin Layer Drying 27
2.13 Thin Layer Drying Models 28
2.13.1 Theoretical Models 29
2.13.2 Semi-Theoretical Models 29
2.14 Goodness of Fit Statistics For Thin Layer Drying Models 37
2.14.1 Root Mean Square Error (Rmse) 37
2.14.2 Mean Sum of Squares of Errors (Mse) Or (Χ2) 38
2.14.3 Coefficient of Determination (R2) 38
2.15 Proximate Analysis 39
2.16 Phytochemical Analysis 39
2.16.1: Flavonoids 39
2.16.2: Terpenoid 39
2.16.3: Phenol 39
2.17: Important of Phytochemicals 39
CHAPTER THREE: MATERIALS AND METHODS
3.0 Materials And Methods 41
3.1 Experimental Material Selection And Preperation 41
3.2 Experimental Treatment 41
3.3 Experimental Set-Up And Procedures 42
3.3.1 Active Solar Drying Method 42
3.3.2:General Observations During Solar Drying 43
3.3.3 Cabinet Drying Method 43
3.3.4 General Observations During Cabinet Drying 44
3.4 Experimental Design 44
3.4.1 Experimental Design For The Active Solar Drying Method 46
3.4.2 Experimental Design For The Cabinet Drying Method 47
3.5 Moisture Content Determination 48
3.6 Determination of Moisture Ratio (Mr) 48
3.7 Drying Rate Calculation (Dr) 49
3.8 Determination of Effective Moisture Diffusivity 49
3.9 Mathematical Modeling of Drying Kinetics 50
3.9.1 Statistical Evaluation of Drying Models 50
3.10: Proximate Analysis of Ug I And Ug II Dried Samples 53
3.10.1: Determination of Crude Fat Content 53
3.10.2: Determination of Ash Content 54
3.10.3: Determination of Crude Protein 54
3.10.4: Determination of Carbohydrate Content 54
3.11: Phytochemical Analysis of Ug I And Ug II Dried Samples 55
3.11.1: Determination of Terpenoid 55
3.11.2: Total Flavonoid Content 55
3.11.3: Determination of Polyphenol 56
CHAPTER FOUR: RESULTS AND DISCUSSION
4.0: Results And Discussion 57
4.1: Effect of Treatments on Drying Characteristics of Umudike Ginger I And Umudike Ginger II Using Active Solar Dryer 57
4.1.1: Drying Characteristics of Unblanched UG I And UG II Varieties of Ginger Rhizomes 57
4.1.2: Effect Of Blanching Time on the Drying Characteristics of UG I And UG II 59
4.1.3: Drying Rate of UG I And UG II Unblanched 62
4.1.4: Drying rate of blanched UG I and UG II 63
4.1.5: Determination of Effective Moisture Diffusivity for Active Solar Dryer 66
4.1.6: Drying Rate Slope 68
4.1.7: Results of Non-Linear Regression Analysis of the fitting of ten Semi-Theoritical models to thin layer drying Data using Active Solar Dryer 69
4.1.8: Validation of Selected Models for Solar Dried UG I and UG II, Unblanched Respectively 72
4.1.9: Validation of Selected Models for Active Solar Dried UG I and UG II, Blanched 50℃ AT 3, 6 and 9 Minutes, Respectively 75
4.2: Drying Characteristics of UG I And UG II Varieties of Ginger Rhizomes Under Cabinet Dryer 82
4.2.1: Drying Characteristics of Unblanched UG I and UG II Verieties of Ginger Rhizomes 82
4.2.2: Effect of blanching time on drying characteristics of 50℃blanched UG I and UG II 84
4.2.3: Drying Rate of 50℃ Blanched UG I and UG II 88
4.2.4: Determination of Effective Moisture Diffussivity 90
4.2.5: Drying Rate Slope 92
4.2.6: Results of Non-Linear Regression Analysis of the Fitting of Ten Semi-Theoritical Models to Thin layer Dying Data using Cabinet Dryer 93
4.2.7: Validation of Selected Models for Cabinet Dried UG I and UG II, Unblanched Respectively 95
4.2.8: Validation of Selected Models for Cabinet Dried UG I and UG II, Blanched 50℃ at 3, 6 and 9 Minutes Respectively 98
4.3: Proximate Analysis of UG I and UG II for Active Solar and Cabinet Dried Samples 105
4.4: Phytochemical Analysis of UG I and UG II for Active Solar and Cabinet Dried Samples 110
4.6: Cost Analysis 113
4.6.1: For Solar Drying 113
4.6.2: For Cabinet Drying 113
4.6.3: Proximate Analysis 114
4.6.4: Phytochemical Analysis 114
4.6.5: Data Analysis And Modelling 114
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.0: Conclusion and Recommendations 115
5.1: Conclusions 115
5.2: Recommendations 116
REFERENCES 117
APPENDICES 129
LIST OF TABLES
Table 2.1: Production In Major Ginger Producing Countries (2014-2018) 8
Table 2.2: Ginger Quality Specifications 10
Table 2.3: Chemical Composition Of Nigeria Ginger Rhizomes 16
Table 2.4: Nutrient/Metabolic Constituents Of Freshly Harvested Ginger Rhizome 17
Table 3.2 Experiments Done To Show Factorial Design (Cabinet Drying) 46
Table 3.1 Experiments Done To Show Factorial Design (Solar Dryer) 47
Table 3.3 Thin Layer Mathematical Models Used 52
Table 4.1 Unblanched and Blanched UG I and UG II 67
Table 4.2 Unblanched and Blanched UG I and UG II Drying Rate Slope 68
Table 4.3 Best fitted Statistical Results Obtained from the Drying Models (Solar Drying) 70
Table 4.4 Unblanched and Blanched UG I and UG II 91
Table 4.5: Unblanched and Blanched UG I and UG II Drying Rate Slope 92
Table 4.6: Best fitted Statistical Results Obtained from the Drying Models (cabinet Drying) 94
Table 4.7: Proximate (nutrients) Contents of UG I and UG II Varieties of Ginger Rhizome, with Various Treatments for Solar Dried Samples 107
Table 4.8: Proximate (nutrients) Contents of UG I and UG II Varieties of Ginger Rhizome, with Various Treatments for Cabinet Dried Samples 109
Table 4.9: Phytochemical (nutrients) Contents of UG I and UG II Varieties of Ginger Rhizome, with Various Treatments for Solar Dried Samples 111
Table 4.10: Phytochemical (nutrients) Contents of UG I and UG II Varieties of Ginger Rhizome, with Various Treatments for Cabinet Dried Samples 112
LIST OF FIGURES
Fig. 2.1 Constant And Falling Rate Periods In Thin-Layer Drying Of High Moisture Grain 23
Fig 4.1 Effect of peeling on the drying characteristics of UG I and UG II (a) whole peeled 58
Fig 4.2 Effect of peeling on the drying characteristics of UG I and UG II (b) whole unpeeled 58
Fig 4.3 Effect of spliting on the drying characteristics of UG I and UG II (c) split peeled 58
Fig 4.4 Effect of spliting on the drying characteristics of UG I and UG II (d) split unpeeled 58
Fig 4.5 Effect of blanching time on the drying characteristics of Whole peeled UG I 60
Fig 4.6 Effect of blanching time on the drying characteristics of Whole peeled UG II 60
Fig 4.7 Effect of blanching time on the drying characteristics of Whole unpeeled UG I 60
Fig 4.8 Effect of blanching time on the drying characteristics of Whole unpeeled UG II 60
Fig 4.9 Effect of blanching time on the drying characteristics of Split peeled UG I 60
Fig 4.10 Effect of blanching time on the drying characteristics of Split peeled UG II 60
Fig 4.11 Effect of blanching time on the drying characteristics of Split unpeeled UG I 61
Fig 4.12 Effect of blanching time on the drying characteristics of Split unpeeled UG II 61
Fig. 4.13 Effect of peeling on drying rate of Whole peeled UG I and UG II 63
Fig. 4.14 Effect of peeling on drying rate on drying time at Whole unpeeled UG I 63
Fig. 4.15 Effect of splitting on drying rate of Split peeled UG I and UG II 63
Fig. 4.16 Effect of splitting on drying rate of Split unpeeled UG I and UG II 63
Fig 4.17 Effect of blanching on drying rate and drying time of Whole peeled UG I 63
Fig 4.18 Effect of blanching on drying rate and drying time of Whole peeled UG II 63
Fig 4.19 Effect of blanching on drying rate and drying time of Whole unpeeled UG I 64
Fig 4.20 Effect of blanching on drying rate and drying time of Whole unpeeled UG II 64
Fig 4.21 Effect of blanching on drying rate and drying time of Split peeled UG I 64
Fig 4.22 Effect of blanching on drying rate and drying time of Split peeled UG II 64
Fig 4.23 Effect of blanching on drying rate and drying time of Split unpeeled UG I 64
Fig 4.24 Effect of blanching on drying rate and drying time of Split unpeeled UG II 64
Fig. 4.25 Drying Parameter Values For Solar Drying 65
Fig. 4.26 Solar Meter Reading For Sun Intensity 65
Fig 4.27: Comparison Of Experimental And Predicted Moisture Ratio Values By Two-Term Model For Whole Peeled Ug I Unblanched For Solar Drying 73
Fig 4.28: Comparison Of Experimental And Predicted Moisture Ratio Values By Two-Term Model For Whole Peeled Ug II Unblanched For Solar Drying 73
Fig 4.29: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Unpeeled Ug I Unblanched For Solar Drying 73
Fig 4.30: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Unpeeled Ug II Unblanched For Solar Drying 73
Fig 4.31: Comparison Of Experimental And Predicted Moisture Ratio Values By Two-Term Model For Split Peeled Ug I Unblanched For Solar Drying 73
Fig 4.32: Comparison Of Experimental And Predicted Moisture Ratio Values By Midilli And Kucuk Model For Split Peeled Ug II Unblanched For Solar Drying 73
Fig 4.33: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Split Unpeeled Ug I Unblanched For Solar Drying 74
Fig 4.34: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Split Unpeeled Ug II Unblanched For Solar Drying 74
Fig 4.35: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug I (Blanched 50℃ At 3mins) For Solar Drying 75
Fig 4.36: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug II (Blanched 50℃ At 3mins) For Solar Drying 75
Fig 4.37: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug I (Blanched 50℃ At 3mins) For Solar Drying 75
Fig 4.38: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug II (Blanched 50℃ At 3mins) For Solar Drying 75
Fig 4.39: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Peeled Ug I (Blanched 50℃ At 3mins) For Solar Drying 76
Fig 4.40: Comparison Of Experimental And Predicted Moisture Ratio Values By Two-Term Model For Split Peeled Ug II (Blanched 50℃ At 3mins) For Solar Drying 76
Fig 4.41: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Unpeeled Ug I (Blanched 50℃ At 3mins) For Solar Drying 76
Fig 4.42: Comparison Of Experimental And Predicted Moisture Ratio Values By Midilli And Kucuk Model For Split Unpeeled Ug II (Blanched 50℃ At 3mins) For Solar Drying 76
Fig 4.43: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Whole Peeled Ug I (Blanched 50℃ At 6mins) For Solar Drying 76
Fig 4.44: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug II (Blanched 50℃ At 6mins) For Solar Drying 76
Fig 4.45: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug I (Blanched 50℃ At 6mins) For Solar Drying 77
Fig 4.46: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Unpeeled Ug II (Blanched 50℃ At 6mins) For Solar Drying 77
Fig 4.47: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Peeled Ug I (Blanched 50℃ At 6mins) For Solar Drying 77
Fig 4.48: Comparison Of Experimental And Predicted Moisture Ratio Values By Verma Et Al. Model For Split Peeled Ug II (Blanched 50℃ At 6mins) For Solar Drying 77
Fig 4.49: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Unpeeled Ug I (Blanched 50℃ At 6mins) For Solar Drying 77
Fig 4.50: Comparison Of Experimental And Predicted Moisture Ratio Values By Verma Et Al. Model For Split Unpeeled Ug II (Blanched 50℃ At 6mins) For Solar Drying 77
Fig 4.51: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Whole Peeled Ug I (Blanched 50℃ At 9mins) For Solar Drying 78
Fig 4.52: Comparison Of Experimental And Predicted Moisture Ratio Values By Handerson And Pabis Model For Whole Peeled Ug II (Blanched 50℃ At 9mins) For Solar Drying 78
Fig 4.53: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug I (Blanched 50℃ At 9mins) For Solar Drying 78
Fig 4.54: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Unpeeled Ug II (Blanched 50℃ At 9mins) For Solar Drying 78
Fig 4.55: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Peeled Ug I (Blanched 50℃ At 9mins) For Solar Drying 78
Fig 4.56: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Peeled Ug II (Blanched 50℃ At 9mins) For Solar Drying 78
Fig 4.57: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Unpeeled Ug I (Blanched 50℃ At 9mins) For Solar Drying 79
Fig 4.58: Comparison Of Experimental And Predicted Moisture Ratio Values By Verma Et Al. Model For Split Unpeeled Ug II (Blanched 50℃ At 9mins) For Solar Drying 79
Fig 4.59: Effect of peeling on the drying characteristics for Whole peeled UG I and UG II 83
Fig 4.60: Effect of peeling on the drying characteristics for Whole unpeeled UG I and UG II 83
Fig 4.61: Effect of spliting on the drying characteristics for Split peeled UG I and UG II 83
Fig 4.62: Effect of spliting on the drying characteristics for Split unpeeled UG I and UG II 83
Fig 4.63 Effect of blanching time on the drying characteristics for Whole peeled UG I 85
Fig 4.65 Effect of blanching time on the drying characteristics for Whole peeled UG II 85
Fig 4.66 Effect of blanching time on the drying characteristics for Whole unpeeled UG I 85
Fig 4.67 Effect of blanching time on the drying characteristics for Whole unpeeled UG II 85
Fig 4.68 Effect of blanching time on the drying characteristics for Split peeled UG I 85
Fig 4.69 Effect of blanching time on the drying characteristics for Split peeled UG II 85
Fig 4.70 Effect of blanching time on the drying characteristics for Split unpeeled UG I 86
Fig 4.71 Effect of blanching time on the drying characteristics for Split unpeeled UG II 86
Fig. 4.72 Effect of drying rate on drying time at Whole peeled UG I and UG II 88
Fig. 4.73 Effect of drying rate on drying time at Whole unpeeled UG I and UG II 88
Fig. 4.74 Effect of drying rate on drying time at Split peeled UG I and UG II 88
Fig. 4.75 Effect of drying rate on drying time at Split unpeeled UG I and UG II 88
Fig 4.76 Effect of drying rate on drying time at Whole peeled UG I 88
Fig 4.77 Effect of drying rate on drying time at Whole peeled UG II 88
Fig 4.78 Effect of drying rate on drying time at Whole peeled UG II 89
Fig 4.79 Effect of drying rate on drying time at Whole unpeeled UG II 89
Fig 4.80 Effect of drying rate on drying time at Split peeled UG I 89
Fig 4.81 Effect of drying rate on drying time at Split peeled UG II 89
Fig 4.82 Effect of drying rate on drying time at Split unpeeled UG I 89
Fig 4.83 Effect of drying rate on drying time at Split unpeeled UG II 89
Fig 4.84: Comparison Of Experimental And Predicted Moisture Ratio Values By Handerson And Pabis Model For Whole Peeled Ug I (Unblanched) For Cabinet Drying 96
Fig 4.85: Comparison Of Experimental And Predicted Moisture Ratio Values By Handerson And Pabis Model For Whole Peeled Ug II (Unblanched) For Cabinet Drying 96
Fig 4.86: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Unpeeled Ug I (Unblanched) For Cabinet Drying 96
Fig 4.87: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug II (Unblanched) For Cabinet Drying. 96
Fig 4.88: Comparison Of Experimental And Predicted Moisture Ratio Values By Handerson And Pabis Model For Split Peeled Ug I (Unblanched) For Cabinet Drying 96
Fig 4.89: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Peeled Ug II (Unblanched) For Cabinet Drying 96
Fig 4.90: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Unpeeled Ug I (Unblanched) For Cabinet Drying 97
Fig 4.91: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Unpeeled Ug II (Unblanched) For Cabinet Drying 97
Fig 4.92: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug I (Blanched 50℃ At 3mins) For Cabinet Drying 98
Fig 4.93: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Peeled Ug II (Blanched 50℃ At 3mins) For Cabinet Drying 98
Fig 4.94: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug I (Blanched 50℃ At 3mins) For Cabinet Drying 98
Fig 4.95: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug II (Blanched 50℃ At 3mins) For Cabinet Drying 98
Fig 4.96: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Split Peeled Ug I (Blanched 50℃ At 3mins) For Cabinet Drying 99
Fig 4.97: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Peeled Ug II (Blanched 50℃ At 3mins) For Cabinet Drying 99
Fig 4.98: Comparison Of Experimental And Predicted Moisture Ratio Values By Verma Et Al. Model For Split Unpeeled Ug I (Blanched 50℃ At 3mins) For Cabinet Drying 99
Fig 4.99: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Unpeeled Ug II (Blanched 50℃ At 3mins) For Cabinet Drying 99
Fig 4.100: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Whole Peeled Ug I (Blanched 50℃ At 6mins) For Cabinet Drying 99
Fig 4.101: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug II (Blanched 50℃ At 6mins) For Cabinet Drying 99
Fig 4.102: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug I (Blanched 50℃ At 6mins) For Cabinet Drying 100
Fig 4.103: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Whole Unpeeled Ug II (Blanched 50℃ At 6mins) For Cabinet Drying 100
Fig 4.104: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Peeled Ug I (Blanched 50℃ At 6mins) For Cabinet Drying 100
Fig 4.105: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Split Peeled Ug II (Blanched 50℃ At 6mins) For Cabinet Drying 100
Fig 4.106: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Unpeeled Ug I (Blanched 50℃ At 6mins) For Cabinet Drying 100
Fig 4.107: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Unpeeled Ug II (Blanched 50℃ At 6mins) For Cabinet Drying 100
Fig 4.108: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug I (Blanched 50℃ At 9mins) For Cabinet Drying 101
Fig 4.109: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Whole Peeled Ug II (Blanched 50℃ At 9mins) For Cabinet Drying 101
Fig 4.110: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug I (Blanched 50℃ At 9mins) For Cabinet Drying 101
Fig 4.111: Comparison Of Experimental And Predicted Moisture Ratio Values By Demir Et Al. Model For Whole Unpeeled Ug II (Blanched 50℃ At 9mins) For Cabinet Drying 101
Fig 4.112: Comparison Of Experimental And Predicted Moisture Ratio Values By Hii Et Al. Model For Split Peeled Ug I (Blanched 50℃ At 9mins) For Cabinet Drying 101
Fig 4.113: Comparison Of Experimental And Predicted Moisture Ratio Values By Henderson And Pabis Model For Split Peeled Ug II (Blanched 50℃ At 9mins) For Cabinet Drying 101
Fig 4.114: Comparison Of Experimental And Predicted Moisture Ratio Values By Logarithmic Model For Split Unpeeled Ug I (Blanched 50℃ At 9mins) For Cabinet Drying 102
Fig 4.115: Comparison Of Experimental And Predicted Moisture Ratio Values By Verma Et Al. Model For Split Unpeeled Ug II (Blanched 50℃ At 9mins) For Cabinet Drying 102
LIST OF PLATES
Plate 1a: A pictorial view of an active solar dryer used for the experiment 167
Plate 1b: A pictorial view of an active solar dryer being prepared for the experiment 168
Plate 1.1: UG I and UG II unblanched samples with various treatments (whole peeled, whole unpeeled, split peeled, and split unpeeled) using a solar dryer. 169
Plate 1.2: UG I and UG II blanched samples @ 50oC for 3minutes, 6minutes, and 9minutes respectively for the various treatments (whole peeled, whole unpeeled, split peeled, and split unpeeled) using the solar dryer. 170
Plate 2a: A pictorial view of a cabinet dryer used for the experiment 171
Plate 2b: A pictorial view of a cabinet dryer with a stove as a source of heat used for the experiment 171
Plate 2c: A pictorial view of heat regulation in the drying chamber using a thermometer. 172
Plate 2d: A pictorial view of UGI and UGII samples loaded into the cabinet dryer's drying chamber. 172
Plate 2.1: UG I and UG II unblanched samples with various treatments (whole peeled, whole unpeeled, split peeled, and split unpeeled) using a cabinet dryer. 173
Plate 2.2: UG I and UG II blanched samples @ 50oC for 3minutes, 6minutes, and 9minutes respectively for the various treatments (whole peeled, whole unpeeled, split peeled, and split unpeeled) using cabinet dryer. 174
Plate 2.3: A pictorial view for the observation of readings being taken after 1hour intervals. 175
Plate 3: A pictorial view of digital water barth, used for blanching. 176
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF STUDY
Ginger remains the most basic and essential medicinal spices in the world (Prabhakaran, 2013). It is one of the oldest of all the spices and condiments that have been under cultivation for millennia in many parts of the world (Spore, 1992; Guwo, 2008).
Nigeria is among the major producers and exporters of ginger globally, with an annual production of about 160,000 metric tons (MT) on 48,910 hectares, which is 7.9% of world production (FAO, 2013). Although, it is grown in some States of Nigeria, namely Kaduna, Nasarawa, Benue, Niger, and Gombe. Southern Kaduna in Kaduna State, is the main producing zone with over 95% of the country’s total production (Okafor, 2002). According to Fumen et al. (2003) and Yiljep et al. (2005), the two popular ginger varieties produced in the country are the ‘Tafin-Giwa,’ a yellowish variety with plump rhizomes, and ‘Yatsun-Biri,’ which is black variety and has small compact rhizomes. Ginger has in abundant volatile and fixed oil, as well as pungent compounds, minerals, resins, starch and protein. (Ravindran and Nirmal, 2005). Ginger has a proximate composition of 3-6 percent of fatty oil, 9 percent protein, 60-70 percent carbohydrate, 3-8 percent fiber, 8 percent ash, 12 percent water, and 2-3 percent volatile oil (Alakali and Satimehin, 2009). Dry ginger contains 1-3 percent essential oil, 5-10 percent oleoresin, 50-55 percent starch, 7-12 percent moisture, and small amounts of protein, carbohydrate, fats, and ash as stated by Eze and Agbo (2011) This accounts for the increased demand of Nigerian ginger in the international market.
Drying is a useful food preservation method widely practiced globally. It is the act of extracting the moistness in a product up to a specific threshold value by evaporation. In this way, the product can be stored for an extended period to decrease the product's water activity, reduces microbiological activity, and minimizes physical and chemical changes encountered when stored (Darvishi and Hazbavi, 2012).
The method of drying in a thin layer of sample particle is known as thin layer drying (Panchariya et al., 2002). It is also a portion of sample that’s fully exposed to air during drying; The layer’s depth (thickness) should be consistent, without exceeding three layers of particles (ASAE, 1999). The aim is to minimize deterioration and microbial spoilage by reducing the water level to a certain threshold. Doungporn et al. (2012) reported that Fick’s second law is usually used to explain liquid diffusion theory, which describes agricultural products' drying phenomenon when employing thin-layer drying equations.
1.2 STATEMENT OF PROBLEM
Research carried out by Eze and Agbo (2011) showed that ginger drying at a temperature above 70℃ appears to reduce its protein and change its organoleptic attributes by lossing its aroma and also colour variation. The antioxidant properties of ginger, which are obtained from the amounts of oleoresin and polyphenols present in it, have been linked to its medicinal value (Eleazu and Eleazu, 2012). The majority of the ginger grown in Nigeria is processed and exported as ginger dried powder, or ginger split dried and extracts.
As cooling is not a viable option to extend ginger's life shelf, an alternative is drying and operations of dryers and improving the existing drying systems. The goal of modern drying nowadays is to minimize the consumption of energy and providing a high quality of product with a minimal increase in economic inputs, which is attracting an increasing number of applications in the drying process (Darvishi et al.,2013). New drying methods are studied to minimize the drying time and energy consumption without changing their quality. In the past six decades, the study of drying behaviour of different materials has been the subject of interest for various investigators on theoretical and practical grounds (Mohammadi et al., 2008). Models like Newton, Page, Henderson and Pabis, Midilli-Kcuk, and Wang-Singh are commonly applied. Different models established, have been applied on many crops by researchers, and the best fitted selected to represent such crop's drying kinetic behaviour. Every crop has its own distinct drying behavioural pattern and is usually predicted by a particular drying model using some statistical indicators. The best model can then be applied in designing dryers and processing of that product. The knowledge of the changes in agricultural products characteristics when subjected to drying process is of fundamental importance for correct storage, processing and the design, fabrication, and operation of equipment applied during the post-harvest processing of these products (Bleoussi et al., 2010). Thereby, it improves food productivity, reduces heavy post-harvest losses, and increases the farmers’ income by recommending the best drying method for preserving ginger rhizomes. Thus, there is a great need to clearly understand the drying principles and estimate the energy needed to dry ginger rhizomes using the drying method of thin layer drying.
1.3 OBJECTIVES OF THE STUDY
This work’s general objective is to carry out Mathematical modelling of thin layer drying kinetics of ginger rhizome using active solar energy and cabinet dryer.
The specific objectives are to:
i. Determine the drying kinetics using the active solar dryer and cabinet dryer to dry UG I and UG II varieties of ginger.
ii. Determine the effects of treatment, blanched and unblanched for [Split (peeled and unpeeled), Whole (peeled and unpeeled)] on the drying of ginger rhizomes.
iii. To select and evaluate a thin layer model for the solar and cabinet dried ginger rhizomes.
iv. To develop empirical prediction equations for thin-layer drying of UG I and UG II.
1.4 JUSTIFICATION OF THE STUDY
At present, the majority of Nigerian ginger is exported in split-dried form, where it is processed into industrial products such as ginger powder, essential oils, and oleoresin by importing countries. The processed products are imported into the country at a higher cost (Yiljep et al., 2005; Meadows, 1988), underscoring the important of processing Nigerian ginger industrially.
Production of ginger is seasonal while consumption is all year round, and therefore there is a great need to cut down on post-harvest losses by processing them into dried forms. A reduced moisture content increases shelf life. Therefore, it prevents excessive post-harvest losses that generally occurred during storage. No work on modelling of ginger drying behaviour, during their water removal stage has been published. Effort of most researches have been channelled mainly on physical and mechanical properties. As a result, much is not known about ginger's behavioral pattern during the period of drying. The drying of most fruits and other agricultural products has gained successful prediction using mathematical models (Mohammadi et al., 2008).
As part of a more extensive food processing programme directed toward village-level entrepreneurs, drying of ginger can increase supply, improve seasonal food choice, generate income, and decrease excessive dependence on imported processed ginger (George et al., 2007).
Experimental and analytical studies of thin layer process of drying are essential for performance improvements of drying systems (Alibas, 2012). Many countries dry vast amounts of food to extend their shelf-life, reduce packaging costs, reduce shipping weights, boost appearance, encapsulate original taste, and keep nutritional value (Gunhan et al., 2010). Imagine what happens when the dryers are improperly produced, the objective of drying will not be achieved, and the product quantity and quality would be compromised.
Research have shown that relying solely on experimental practices of drying without a good knowledge of the drying kinetics, can have a major impact on dryer performance, increase production cost, and reduce the dried product quality (Rayaguru and Routray, 2012). The agricultural loss in post-harvest production can be minimized significantly by using proper drying techniques with knowledge and data gotten from an experimental investigation of drying kinetics of agricultural products.
1.5 SCOPE OF STUDY
This thesis work covers the thin-layer drying kinetics of UG I and UG II varieties of ginger, using two drying methods. Ten models for thin layer drying process, were evaluated to determine the best suitable model.
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