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
Title page
Table of contents
Abstract
List of tables and figures
Chapter one: Introduction
1.1 Background study
1.2 Statement of problems
1.3 Objectives of study
1.4 Significance of study
Chapter two: Literature review
2.1 History of tigernuts
2.2 Botany of tigernuts
2.3 Ecology of tigernuts
2.4 Nutritional composition of tigernuts
2.5 Importance of tigernuts and its products
2.5.1 Nutritional and health importance
2.5.2 Economic importance
2.6 Antinutrient factor and toxicity of tigernuts
2.7 Some properties of tigernuts and its products
2.8 Handling and keeping quality of tigernuts
2.9 Utilization of tigernuts
2.10 Processing techniques
Chapter three: Materials and methods
3.1 Collection of samples
3.2 Sample preparation and analyses
3.2.1 Sample preparation
3.2.1.1 Fresh tigernuts
3.2.1.2 Tigernut milky juice extract
3.2.1.3 Fermented tigernut milky juice
3.2.1.4 Malted tigernut
3.2.1.5 Dried tigernut
3.2.1.6 Roasted tigernuts
3.2.2. Proximate composition analyses
3.2.2.1 Moisture content
3.2.2.2 Crude protein content
3.2.2.3 Mineral ash content
3.2.2.4 Crude fat content
3.2.2.5 Crude fiber content
3.2.2.6 Carbohydrate content
3.2.3.7 Energy value
3.2.3 Mineral and vitamin content analyses of tigernuts(treaated and untreated)
3.2.3.1 Mineral content analyses (Mg, K, P, Ca, Fe, Cu & Zn)
3.2.3.2 Vitamin content (vitamin C & E)
3.2.4 Physico-chemical and functional properties analyses
3.2.4.1 pH
3.2.4.2 Specific gravity
3.2.4.3 Viscosity
3.2.4.4 Foaming capacity and stability
3.2.4.5 Emulsion capacity and stability
3.2.4.6 Ethanol content of fermented tigernut milky juice
3.2.4.7 Total available reducing sugar of tigernut milk and wine
3.2.5 Development of tigernut products (milk, coffee and wine)
3.2.5.1 Tigernut milk (unfermented tigernut beverages)
3.2.5.2 Tigernut coffee (coffee and cocoa substitute)
3.2.5.3 Tigernut wine (fermented tigernut beverages)
3.2.7 Vitamin and zinc content of tigernut milk and wine
3.2.8 Organoleptic properties and general acceptability assessment
3.2.9 Microbial count and keeping quality assessment
3.3 Statistical analyses
Chapter four: Results
4.1 Proximate composition and energy value of tigernuts
4.2 Effect of processing on the proximate composition and energy value
4.3 Percentage changes on the proximate composition and energy value of tigernuts due to processing effects
4.4 Mineral and vitamin content of tigernuts
4.5 Effect of processing on the mineral content of tigernuts
4.6 Percentages on the mineral content of tigernuts due to processing effects
4.7 Physico-chemical and functional properties and its products
4.8 Vitamin and zinc content of tigernut milk and wine
4.9 Organoleptic evaluation of tigernut milk (unfermented beverages)
4.10 Organoleptic evaluation of tigernut coffee (coffee and cocoa substitute)
4.11 Organoleptic evaluation of tigernut wine (fermented beverages)
4.12 Microbial count of tigernut products (milk and wine)
4.13 Keeping quality of tigernut products (milk, coffee and wine)
Chapter five: Discussion
5.1 Nutritional value of tigernuts as widely consumed raw
5.2 Effect of processing on the nutritional composition of tigernuts
5.3 Physico-chemical and functional properties and its products
5.4 Organoleptic properties of tigernut products (milk, coffee and wine)
5.5 Vitamin and zinc content of tigernut milk and wine
5.6 Microbial count and keeping quality of tigernut products
5.7 Conclusion
5.8 Recommendations and suggestions
References
Appendices
Appendix
CHAPTER ONE
1. Introduction
1.1 Background study
Tigernut (Cyperus esculentum) is a perennial grass-like plant with spheroid tubers, pale yellow cream kernel surrounded by a fibrous sheath. It is also known as yellow nut sedge, earth or ground almonds, “souchet” in French, “ermandeln” in German and “chufa” in Spanish (TTSL, 2005). Grossman and Thomas (1998) reported that chufa came to Spain from Africa. Tigernut is found wild and cultivated in Africa, South America, Europe and Asia. Tigernuts grow in the wild, along rivers and are cultivated on a small scale by rural farmers mostly in the northern states of Nigeria. It is locally called “aya” in Hausa; “aki awusa” in Igbo; “ofio” in Yoruba and “isipaccara” in Effik. Tigernuts are edible, sweet, nutty, flavoured tubers which contain protein, carbohydrate, sugars, and lots of oil and fiber (FAO, 1988). Grossman and Thomas (1998) showed that tigernuts have been cultivated for food and drink for men and planted for hogs for many years in Spain and that the lovely milky elixir is served in health Spas, Pubs, and Restaurants as a refreshing beverage (competing successfully with other soft drinks). Unfortunately, despite these potentials in tigernuts it has been a neglected crop in Nigeria. This probably may be due to inadequate knowledge on its production, utilization and nutritional value.
Tigernut could provide a basis for rural industries in Africa. It is an important food crop for certain tribes in Africa, often collected and eaten raw, baked as a vegetable, roasted or dried and ground to flour. The ground flour is mixed with sorghum to make porridge, ice-cream, sherbet or milky drink. It is mostly consumed raw as snack without knowledge of the food and nutritional quality (FAO, 1988). It has also been found to possess good therapeutic quality (Moore, 2004; Zimmerman, 1987; Farre, 2003; Bixquert, 2003; Valls, 2003). Moore stated that “the expansion of tigernut milky drinks will significantly help the research linking tigernut milk to healthier cholesterol levels and other non-dairy manufacturers. This could also gain a boost from an increased consumer interest in health foods”.
Variety of food products can be derived from tiger nut tubers though there is little documentation at large. Various food processing techniques can be applied to tiger nut processing to modify its appearance, develop its natural flavour, stimulate the digestive juices, add variety to the menu, make it easily digestible and bio-available, destroy harmful microorganisms, improve its nutritional quality and prevent decomposition. This project work
1.2 Statement of problems
Food insecurity continues to threaten large proportions of households in low income countries. In view of the operational definition of household food security stated by ACC / SCN (1991), a household is food secure when it has access to the food needed for a healthy life for all its members (adequate in terms of quality, quantity, safety and culturally acceptable), and when it is not at undue risk of losing such access. Adequate nutrition is essential for individual development, activity, good health, fulfillment function and success in societies and nations (ACC / SCN, 1991). Some of the factors that may affect food security as well as nutrition are as follows:
• Inadequate production and knowledge of the food use
• Poor processing, preservation and storage techniques
• Poor infrastructure, especially poor housing, sanitation and storage facilities, education, communications, and transporting systems.
• Poverty
• Extreme imbalances in food or population ratio
• War / political or civil unrest
• Rapid depletion of natural resources
• Cultural attitudes toward certain foods
• High external debt
• Seasonal factors or climatic variations
• Food prices
Tigernut has been for many years one of the underutilized food crops in Nigeria. It is mostly eaten raw as snack and un-identified as a very important food crop that has great potential in managing, preventing and eliminating malnutrition (macronutrient and micronutrient deficiencies) or food insecurity problems. It has been demonstrated by nutritionist that the major nutritional problems could be solved through exploitation of the nutrition and economic potentials of the local food resources. Tigernut is one of the under utilized tubers with great potentials for domestic and commercial purposes. There is no documentation of a successful product made from tigernuts in the Nigerian market. A
There is little documentation on the nutritional quality and versatility of tigernuts in food preparation despite its availability. However, tigernut is still one of the least popular tubers in Nigeria and hence the need for this research which intends to evaluate, promote production and utilization of tiger nuts using various processing techniques.
1.3 Objectives of study
The broad objective of this study is to evaluate the food potentials of tigernut tubers (tigernuts) and its products.
Specific objectives are as follows: to
1) determine the proximate, mineral, vitamin, physico-chemical and functional properties of tigernuts.
2) develop products from tiger nuts using traditional processing techniques such as natural fermentation, malting, drying and roasting.
3) assess the organoleptic properties and general acceptability of the developed tigernut products (milk, coffee and wine beverages).
4) determine some nutritional properties and microbial load of developed tigernut products (milk, coffee and wine beverages).
1.4 Significance of study
In recent years, the need to increase the production and utilization of locally available food resources has been highlighted at different national and international fora. Tigernuts, one of the under utilized food crops locally available in Nigeria could be demonstrated to aid in solving major nutritional problems through exploitation of its nutritional and economic potentials.
The results of this study will provide a baseline data on tigernut utilization. This will go a long way to diversify its use and in turn lead to its increased production both at household and national levels ultimately to ensure food security. Furthermore, it is expected that through the knowledge of its composition, tiger nut may be exploited for use in the prevention and treatment of some non communicable diseases for example cancers, diabetes, heamorrhoids and cardiovascular diseases......
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