Evaluation of Food Potentials of Tigernut Tubers (Cyperus Esculentus) and Its Products (Milk, Coffee and Wine)

ABSTRACT The food potentials of tigernut tubers (Cyperus esculentus) locally know as “aki awusa” in Igbo, ”aya” in Hausa and “ofio” in Yoruba were evaluated. The proximate composition of 100g of raw and processed tigernuts showed that moisture content of tigernuts ranged from 4.19 – 51.93 %, crude protein 2.61 – 10.12 %, ash 0.70 – 1.77 %, crude fibre 7.48 – 13.97 %, crude fat 10.79 – 32.06 %, and carbohydrate 22.73 – 56.85 %. Energy values ranged from 232.31- 487.15 Kcal. Tigernuts contain significant amounts of Mg (95.32 -140.96 mg), K (106.44 – 427.92 mg), P (121.78 – 195.95 mg), Fe (1.60 – 4.03 mg), Cu (0.08 – 0.99 mg), Zn (0.32 - 2.46mg), vitamin C (30.90 – 84.66 mg), vitamin E (2.22 – 5.26 mg), moderate Ca (24.42 – 62.29 mg) and low Na (15.77 – 18.27 mg) content. Processing of tigernuts generally increased carbohydrate but decreased magnesium and sodium values. Malting significantly increased calcium content (85 %) and drying and roasting increased Zn and Cu by 100 %. Physico-chemical and functional properties showed that tigernuts and its products are acidic while viscosity of the products per 100 ml was between 88 – 90 cP, specific gravity 1.01 – 1.07, reducing sugar 0.30 – 0.44 g , foaming capacity 18 %. Foaming stability 5.35 %, emulsion capacity 21.88 %, and emulsion stability 49.38 %. Alcohol content of tigernut wine was between 3.17 – 7.13 %. Fresh tigernuts were utilized in the development of tigernut products (milk, coffee and wine) using household methods such as soaking, drying, roasting, malting, fermentation and freezing. Organoleptic and acceptability assessment of the developed tigernut products showed that there was no significant difference (P > 0.05) between tiegrnut products and their controls in most of the parameters tested. All then products were highly acceptable. Tigernuts products (milk extract and wine) evaluation per 100 ml showed high ascorbic acid (6.18 – 7.8 mg), thiamin (0.80 – 1.25 mg), riboflavin (0.35 – 0.59 mg), vitamin E (0.22 – 0.75 mg) and cyanocobalamin (0.03 – 0.05 ug) content. The result of the microbial count of tigernut products (milk and wine) showed values between 3.0 x 102 – 8.0 x 102 cfu / ml and keeping quality ranged from 6 hours to 10 months.

Table of contents Page

Title page - - - - - - - - - - i

Approval page - - - - - - - - - ii

Certification -` - - - - - - - - - iii

Dedication - - - - - - - - - - iv

Acknowledgement - - - - - - - - - v

Table of contents - - - - - - - - - vi

Abstract - - - - - - - - - - ix

Table of contents - - - - - - - - - vi

List of tables and figures - - - - - - - - ix

Chapter one: Introduction

1.1 Background study - - - - - - - - 1

1.2 Statement of problems - - - - - - - - 2

1.3 Objectives of study - - - - - - - - 3

1.4 Significance of study - - - - - - - - 3

Chapter two: Literature review

2.1 History of tigernuts - - - - - - - - 4

2.2 Botany of tigernuts - - - - - - - - 4

2.3 Ecology of tigernuts - - - - - - - - 6

2.4 Nutritional composition of tigernuts - - - - - - 7

2.5 Importance of tigernuts and its products - - - - - - 9

2.5.1 Nutritional and health importance - - - - - - 9

2.5.2 Economic importance - - - - - - - - 12

2.6 Antinutrient factor and toxicity of tigernuts - - - - - 14

2.7 Some properties of tigernuts and its products - - - - - 15

2.8 Handling and keeping quality of tigernuts - - - - - 16

2.9 Utilization of tigernuts - - - - - - - - 17

2.10 Processing techniques - - - - - - - - 19

Chapter three: Materials and methods

3.1 Collection of samples - - - - - - - - 22

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3.2 Sample preparation and analyses - - - - - - - 22

3.2.1 Sample preparation - - - - - - - - 22

3.2.1.1 Fresh tigernuts - - - - - - - - 22

3.2.1.2 Tigernut milky juice extract - - - - - - - 22

3.2.1.3 Fermented tigernut milky juice - - - - - - 23

3.2.1.4 Malted tigernut - - - - - - - - 23

3.2.1.5 Dried tigernut - - - - - - - - - 24

3.2.1.6 Roasted tigernuts - - - - - - - - 24

3.2.2. Proximate composition analyses - - - - - - 24

3.2.2.1 Moisture content - - - - - - - - 25

3.2.2.2 Crude protein content - - - - - - - - 25

3.2.2.3 Mineral ash content - - - - - - - - 25

3.2.2.4 Crude fat content - - - - - - - - 26

3.2.2.5 Crude fiber content - - - - - - - - 26

3.2.2.6 Carbohydrate content - - - - - - - - 27

3.2.3.7 Energy value - - - - - - - - - 27

3.2.3 Mineral and vitamin content analyses of tigernuts(treaated and untreated) - 27

3.2.3.1 Mineral content analyses (Mg, K, P, Ca, Fe, Cu & Zn) - - - 27

3.2.3.2 Vitamin content (vitamin C & E) - - - - - - 30

3.2.4 Physico-chemical and functional properties analyses - - - - 31

3.2.4.1 pH - - - - - - - - - - 31

3.2.4.2 Specific gravity - - - - - - - - 32

3.2.4.3 Viscosity - - - - - - - - - 32

3.2.4.4 Foaming capacity and stability - - - - - - 33

3.2.4.5 Emulsion capacity and stability - - - - - - 33

3.2.4.6 Ethanol content of fermented tigernut milky juice - - - - 34

3.2.4.7 Total available reducing sugar of tigernut milk and wine - - - 34

3.2.5 Development of tigernut products (milk, coffee and wine) - - - 34

3.2.5.1 Tigernut milk (unfermented tigernut beverages) - - - - 35

3.2.5.2 Tigernut coffee (coffee and cocoa substitute) - - - - - 36

3.2.5.3 Tigernut wine (fermented tigernut beverages) - - - - 37

3.2.7 Vitamin and zinc content of tigernut milk and wine - - - - 38

3.2.8 Organoleptic properties and general acceptability assessment - - - 41

3.2.9 Microbial count and keeping quality assessment - - - - 42

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3.3 Statistical analyses - - - - - - - - 42

Chapter four: Results

4.1 Proximate composition and energy value of tigernuts - - - - 43

4.2 Effect of processing on the proximate composition and energy value - - 45

4.3 Percentage changes on the proximate composition and energy value of tigernuts due to

processing effects - - - - - - - - - 47

4.4 Mineral and vitamin content of tigernuts - - - - - - 49

4.5 Effect of processing on the mineral content of tigernuts - - - - 51

4.6 Percentages on the mineral content of tigernuts due to processing effects - 53

4.7 Physico-chemical and functional properties and its products - - - 55

4.8 Vitamin and zinc content of tigernut milk and wine - - - - 57

4.9 Organoleptic evaluation of tigernut milk (unfermented beverages) - - 59

4.10 Organoleptic evaluation of tigernut coffee (coffee and cocoa substitute) - 61

4.11 Organoleptic evaluation of tigernut wine (fermented beverages) - - 63

4.12 Microbial count of tigernut products (milk and wine) - - - - 65

4.13 Keeping quality of tigernut products (milk, coffee and wine) - - - 65

Chapter five: Discussion

5.1 Nutritional value of tigernuts as widely consumed raw - - - - 67

5.2 Effect of processing on the nutritional composition of tigernuts - - - 69

5.3 Physico-chemical and functional properties and its products - - - 73

5.4 Organoleptic properties of tigernut products (milk, coffee and wine) - - 75

5.5 Vitamin and zinc content of tigernut milk and wine - - - - 77

5.6 Microbial count and keeping quality of tigernut products - - - 78

5.7 Conclusion - - - - - - - - - 80

5.8 Recommendations and suggestions - - - - - - 81

References - - - - - - - - - 83

Appendices - - - - - - - - - 89

Appendix 1 Tables 2.1 - 2.4 - - - - - - - - 89

Appendix 2 Flow diagram 3.1 – 3.3 - - - - - - - 91

Appendix 3 Sensory evaluation / General acceptability form A – C - - - 94

Appendix 4 Recipe for soya bean milk and instant coffee product samples - - 98