TABLE OF CONTENTS
Title page – – – – – – – – i
Approval page – – – – – – ii
Certification – – – – – – – – iii
Dedication – – – – – – – – iv
Acknowledgements – – – – – – – – v
Table of contents – – – – – – –
List of tables – – – – – – – – vi
List of figures – – – – – – vii
List of appendices – – – – – – – – viii
ABSTRACT – – – – – – – – xii
CHAPTER ONE: INTRODUCTION – – – – – 1
1.1 Statement of the problem – – – – – – – 3
1.2 Objectives of the study – – – – – – – 4
1.3 Significance of the study – – – – – – – 4
CHAPTER TWO: LITERATURE REVIEW – – – — 6
2.1 Legumes in human nutrition – – – – – 6
2.2 Functional properties of legumes – – – – – – 7
2.3 Legumes in diet-related non communicable disease – 8
2.4 Bean as a legume – – – – – – – 9
2.5 African yam beans (AYB) (Sphenostylis stenocarpa ) – 9
2.5.1 Nutritional/ chemical composition and organoleptic attributes of AYB 10
2.5.2 Antinutrient composition of 3 varieties of African yam bean- 13
2.5.3 Economic importance/uses of AYB – – – 13
2.5.4 Constraints in the use of AYB – – – – – – 14
Hydrogen cyanide (HCN) – – – – – – – 15
Hemagglutinin (Lectins) – – – – – – 15
2.5.5 The antinutrients in AYB – – – – – 15
Phytic acid – – – – – – – – – 16
Tannins – – – – – – – – – 16
Saponins – – – – – – – 16
Trysin inhibitors – – – – – – 17
Oxalates – – – – – – – – – 17
2.5.6 AYB processing methods used – – – – – 18
Roasting – – – – – – – – – 18
Fermentation – – – – – – – – – 18
2.6 Lime – – – – – – – – 20
CHAPTER THREE: MATERIALS AND METHODS – – – 21
3.1 Materials – – – – – – – 21
3.2.1 Preparation of African yam bean (AYB) flour
for gruel and chemical analysis 21
24h fermentation without lime and roasting – – – – 21
24h fermentation with lime and roasting – – – 21
48h fermentation with lime and roasting – – – 21
Roasted only – – – – – – – – – 22
3.2.2 Preparation of gruel from AYB flours – – – 22
3.3 Laboratory analysis – – – – – – 22
3.3.1 Protein determination – – – – – – 23
3.3.2 Fat determination – – – – – – 24
3.3.3 Ash determination – – – – – – – 24
3.3.4 Crude fibre determination – – – – – 25
3.3.5 Carbohydrate – – – – – – – 25
3.3.6 Phytate determination – – – – – 25
3.3.7 Tannins – – – – – – 26
3.3.8 Determination of trypsin inhibitors – – – 27
3.3.9 Oxalic acid determination – – – – 28
3.3.10 Determination of saponins – – – – 29
3.3.11 Hydrocyanic acid determination – – – – 30
3.3.12 Determination of Haemagglutinin by spectrometric method 31
3.3.13 Raffinose and stachyose determination – – 31
3.4 Organoleptic evaluation – – – – – 32
3.5 Statistical analysis – – – – – – 33
CHAPTER FOUR: RESULTS – – – – – – 34
4.1 Proximate
composition of different AYB flours on dry matter basis – –
4.1.1 Protein – – – – – – – 34
4.1.2 Fat – – – – – – – 34
4.1.3 Ash – – – – – – – 34
4.1.4 Crude fibre – – – – – – – 34
4.1.5 Carbohydrate (CHO) – – – – – – 35
4.2 Effect of treatments on the anti nutrient
contents of AYB flour samples –
4.2.1 Phytate – – – – – – – – 35
4.2.2 Tannins – – – – – – – 35
4.2.3 Oxalates – – – – – – – 35
4.2.4 Saponins – – – – – – – 35
4.2.5 Trypsin inhibitors – – – – – – 35
4.3 Effect of treatment on the raffinose, stachyose, heamagglutinins and hydrogen cyanide composition of AYB flours – – –
4.3.1 Raffinose – – – – – – – 37
4.3.2 Stachyose – – – – – – 37
4.3.3 Heamagglutinins – – – – – – 37
4.3.4 Hydrogen cyanide (HCN) – – – – 38
4.4 Organoleptic characteristics of AYB gruel – – –
4.4.1 Colour – – – – – – – 38
4.4.2 Flavour – – – – – – – 39
4.4.3 Consistency – – – – – – 39
4.4.4 Degree of acceptability – – – – – 39
CHAPTER FIVE:DISCUSSION, CONCLUSION AND
RECOMMENDATIONS 41
5.1 Discussion – – – – – – – – –
5.1.1 Effect of processing on the proximate composition of AYB flours –
Protein – – – – – – – – – 41
Fat – – – – – – – – – 41
Crude fibre – – – – – – – – – 41
Carbohydrate – – – – – – – – – 42
5.1.2 Effect of treatments on the anti nutrient composition
Phytate – – – – – – – – – 42
Oxalates – – – – – – – – – 42
Tannin – – – – – – – – – 42
Trypsin inhibitors – – – – – – 43
Effect of processing on the raffinose and stachyose contents of AYB
flours 43
5.1.3 Effect of treatment on the toxic substance composition of AYB flour samples Heamagglutinin – – – – – – 43
Hydrogen cyanide (HCN) – – – – – – – 44
5.1.4 Effect of
treatment on the beany flavour and other organoleptic characteristics of AYB gruel – – – – – – –
Colour – – – – – – – – – 44
Flavour – – – – – – – – – 44
5.2 Conclusion – – – – – – – 45
5.3 Recommendations – – – – – – 45
REFERENCES – – – – – – – 46
APPENDICES – – – – – – – – 53
ABSTRACT
The aim of this study was to determine the effect of different processing methods on the chemical composition of African yam bean (Sphenostylis stenocarpa) flours and the organoleptic properties of it’s gruels. The seeds of cream coloured African yam bean (AYB) and lime were purchased from Oye Igbo-Eze and Ogige Nsukka markets, respectively in Enugu State, Nigeria.The seeds were sorted and divided into 4 equal portions of 1.5kg each. One portion was washed and fermented in tap water at a seed- water ratio of 1:3 (w/v), for 24h. The second portion was fermented in tap water (1:3 w/v) containing 30 tablespoonful of freshly squeezed lime for 24h. The third portion was fermented in tap water containing lime (30 tablespoonful of lime) (1:3 w/v) for 48h. They were separately sundried for 72h and roasted in a hot sauce pan until cracking. The fourth portion (control) was washed, drained and roasted in a hot sauce until cracking. The AYB samples were separately milled into fine flours and stored in separate airtight containers for chemical analysis and gruel preparations. The flour samples were chemically analyzed for proximate, phytate, tannins, oxalates, saponins, trypsin inhibitors, raffinose, stachyose, hemagglutinins and hydrogen cyanide composition using standard laboratory methods. A nine point hedonic scale was used to collect data on sensory and acceptability tests of the gruels. Means and standard deviations were calculated and least significance difference test was used to separate means. The sample that was fermented in tap water containing lime for 48h ranked best generally. The moisture levels for the flours ranged from 3.60-5.00%, protein 19.96-31.87%, fat 3.54-5.23%, ash 2.99-3.89%, crude fibre 4.00-6.01% and carbohydrate 52.72-62.32%. The anti-nutrient values for the flours were: phytate 2.63-2.97mg/g, tannins 0.02-0.04mg/g, trypsin inhibitors 0.45-0.53mg/g, oxalate 0.01-0.03mg/g, the samples had the same saponin level of 0.01mg/100g. Raffinose contents of the samples ranged from 8.25mg-9.22/100g and stachyose (8.48-6.76mg /100g). heamagglutinins ranged from 4.87 – 6.70 mg/100g and hydrogen cyanide ranged from 0.22-0.28mg/g. In the organoleptic studies, the sample that was fermented for 48h was most preferred over others in terms of colour (6.53), the sample that was fermented in lime water for 24h ranked best for flavor (6.57) and the sample that was only roasted ranked best for general acceptability (6.03).
CHAPTER
ONE
- INTRODUCTION
1.1 Background to the study
It is of great importance to know the
nutrient, toxic substance as well as the anti physiological substance composition
and organoleptic properties of locally available foods in any community or
country. Knowledge and use of local foods can help eliminate malnutrition. One
of the problems of planning therapeutic diets with local foods is limited
information on their nutrient composition (Standing Committee on Nutrition
(SCN), 2006). It has been proposed that the fight against malnutrition in
developing countries should be on the use of mixtures of tubers, cereals and
legumes indigenous to them (Nnam, 2003).Urbanization has made people forget
their traditional foods and favour convenient foods which are mostly
nutritionally inadequate and expensive. The most dietary deficit is protein of
high biological value and this was attributed to the high cost of animal
protein (SCN, 2006). Vegetable proteins however complement each other if well
chosen and will have a nutritive value as good as animal protein (Achinewhu
& Akah, 2003; Nnam, 2003; Obiakor, 2008).
Nutrition is coming to the fore
front as a major modifiable determinant of chronic diseases, with scientific
evidence increasingly supporting the view that alterations in diet have strong
effects (both positive and negative) on health throughout life. Dietary
adjustments may not only influence present health, but may determine whether or
not an individual will develop such diseases as diabetes, obesity,
hypertension, certain cancer and cardiovascular disease much later in life
(WHO/FAO, 2003). Rapid change in disease
pattern had occurred as a result of shifts in diet and lifestyle. The urban based Nigerian is shifting from
exercise, intense agrarian life to a more sedentary urban life, with resultant
obesity, diabetes and hypertension. Cheap imported foods, global markets and
socio-cultural changes are placing African traditional diets at distinct
disadvantages. Indigenous diets are being replaced with more refined
carbohydrate fast foods (Ifeyironwa, Eyzaquirre, Matig, & Johns, 2006). In
tackling the multiple problems of food insecurity, nutrition transition and the
double burden of diseases, it is essential to mobilize and employ indigenous
foods like legumes as part of the solution (SCN, 2006). This is because several
studies have reported immense nutritional and health protecting properties of
African indigenous foods such as legumes (Obizoba & Souzey, 1989; Enwere,
1998; Ene-Obong & Carnovale, 1992; SCN, 2006; Okeke, Ene-Obong, Uzuegbunam,
Simon, & Chukwuone, 2009).
For quite some time, legumes were considered
not too important; but now, their food use is increasing with recent
discoveries concerning their many nutritional and health properties
(Pamplona-Roger, 2006).It has been documented that legumes contain 2-3 times
the protein of cereal grains and no other plant food is as rich in protein as
legumes in their natural state (National Academy of Science (NAS), 1997;
Pamplona-Roger, 2006). Water soluble non-starch polysaccharides (NSP) that have
viscous properties occur mostly in legumes and its benefit in the
prevention/management of diabetes and cardiovascular diseases have been
reported (Onyechi, Jude, & Ellis., 1998; Enwere, 1998). One such legume of
interests is African yam bean (Sphenostylis
stenocarpa) (AYB).
African
yam bean (AYB) is an herbaceous leguminous plant occurring throughout tropical
Africa (United States Department of Agriculture (USDA), 2007). It is grown as a
minor crop in association with yam and cassava. AYB serves as security crop; it
has the potential to meet year round protein requirements if grown on a large
scale (World Health Organization (WHO), 2002). African yam bean (AYB) is highly
nutritious with high protein, mineral and fibre content. Its protein content is
reported to be similar to that of some major and commonly consumed legumes. Its
amino acid profile is comparable if not better than those of cowpea, soy bean
and pigeon pea (Obizoba & Souzey, 1989; Ene-Obong & Carnovale, 1992;
Uguru & Madukaife, 2001). It has high metabolic energy, low true protein
digestibility (62.9%), moderate mineral content, the amino and fatty acids
contents are comparable to those of most edible pulses (Nwokolo, 1987; Uguru
& Madukaife, 2000). It has a higher
water absorption capacity when compared to cowpea (Achinewhu & Akah,
2003).
The potential role of AYB in
the management of many aging and chronic non-communicable diseases has been
reported (Enwere, 1998; Nwachi, 2007; Alozie, Udofia, Lawal & Ani, 2009).
In Ghana, the water drained after boiling may be drunk by lactating mothers to
increase their milk production (Klu, Amoatey, Bansa & Kumaga, 2001). The
economic potential of AYB has been recognized, especially in reducing
malnutrition among Africans (Adewale, 2010).
These health benefits can be
marred by the presence of anti- nutrients. Some processing methods however,
such as soaking, boiling, ferment
