TABLE OF CONTENTS
TITLE PAGE – – – – – – – i
APPROVAL PAGE – – – – – – – ii
CERTIFICATION – – – – – – – iii
DEDICATION – – – – – – – iv
ACKNOWLEDGEMENTS – – – – – – v
LIST OF TABLES – – – – – – vii
LIST OF FIGURES – – – – – – viii
ABSTRACT – – – – – – – ix
CHAPTER ONE: INTRODUCTION – – – – 1
1.1 Background of study – – – – – – 1
1.2 Statement of the problem – – – – – 2
1.3 Objectives of study – – – – – – 3
1.3.1 General objective – – – – – – 3
1.3.2 Specific objective – – – – – – 3
1.4 Significance of the study – – – – – 3
CHAPTER TWO: REVIEW OF RELATED LITERATURE – – 4
2.1 Legumes – – – – – – – 4
2.2 Cowpea – – – – – – – 4
2.3 Cowpea leaves and husks (vegetables) – – – 9
2.3.1 Chemical composition of cowpea leaves – – – 10
2.4 Vegetables and their uses – – – – 11
2.5 Nutrient composition of green leafy vegetables – – 12
2.5.1 Moisture content – – – – – – 12
2.5.2 Protein – – – – – – – 12
2.5.3 Ether extract (fat) – – – – – – 13
2.5.4 Vitamins – – – – – – – – 13
2.5.5 Anti nutrient content – – – – – – 13
2.6 Food processing – – – – – – 16
2.6.1 Processing of vegetables – – – – – 16
2.6.2 Blanching – – – – – – – 17
2.6.3 Drying – – – – – – – 17
2.6.4 Effects of processing on nutrient content of leafy vegetables 18
CHAPTER THREE: MATERAILS AND METHODS – – – 20
3.1 Study area – – – – – – 20
3.2 Sampling procedures – – – – – 21
3.3 Focus group discussion – – – – – 22
3.4 Processing of samples – – – – – – 22
3.4.1 Cowpea leaves – – – – – – 22
3.4.2 Cowpea husks – – – – – – 22
3.5 Purchase of foods – – – – – – – 26
3.5.1 Pounded yam preparation – – – – 26
3.6 soup preparation – – – – – – 26
3.7 Chemical analysis – – – – – – – 28
3.7.1 Proximate analysis – – – – – – – 28
3.7.1.1 Moisture – – – – – – – 28
3.7.1.2 Protein – – – – – – – 29
3.7.1.3 Fat – – – – – – – 30
3.7.1.4 Ash – – – – – – – – 30
3.7.1.5 Crude fiber – – – – – – – 30
3.7.1.6 carbohydrate – – – – – – 31
3.7.2 Mineral determination – – – – – – 31
3.7.3 Vitamins (antioxidants) determination – – – -31
3.7.3.1 Beta carotene (retinol) – – – – – – 31
3.7.3.2 Vitamin C – – – – – – 32
3.7.4 Phytochemical screening – – – – – 33
3.7.4.1 Flavonoids – – – – – – – 33
3.7.4.2 Saponins – – – – – – – 33
3.7.4.3 Tannins – – – – – – 33
3.7.5 Anti nutrients – – – – – – – 34
3.7.5.1 Oxalate determination – – – – – – 34
3.7.5.2 Phytate determination – – – – – – – 34
3.7.5.3 Haemaglutinin – – – – – – – 35
3.8 Sensory evaluation – – – – – 36
3.9 Statistical analysis – – – – – – 36
CHAPTER FOUR: RESULTS – – – – – 37
4.1.1 Protein – – – – – – – – 37
4.1.2 Fat – — – – – – – – 37
4.1.3 Ash – — – – – – – – 37
4.1.4 Fiber – – – – – – – – 37
4.1.5 Carbohydrate – – – – – – – 37
4.2.1 Iron – – – – – – – – 38
4.2.2 Zinc – – – – – – – – – 38
4.2.3 Iodine – – – – – – – – – 38
4.2.4 Calcium – – – – – – – – 39
4.2.5 Phosphorus – – – – – – – – 39
4.2.6 Bet carotene – – – – – – – 39
4.2.7 Vitamin – – – – – – – – 39
4.3.1 Tannins – – – – – – – – 40
4.3.2 Saponins – – – – – – – 40
4.3.3 Flavonoids – – – – – – 40
4.3.4 Polyphenols – – – – – – – 41
4.4.1 Phytate – – – – – – – 41
4.4.2 Oxalate – – – – – – – 41
4.4.3 Haemagglutinin – – – – – – – 42
4.5.1 Protein – – – – – – – – 42
4.5.2 Fat – – – – – – – – 42
4.5.3 Ash – – – – – – – – – 43
4.5.4 Fibre – – – – – – – – 43
4.5.5 Carbohydrate – – – – – – – – 43
4.6.1 Iron – – – – – – – – – 43
4.6.2 Zinc – – – – – – – – 44
4.6.3 Calcium – – – – – – – 44
4.6.4 Iodine – – – – – – – – 44
4.6.5 Phosphorus – – – – – – – 44
4.6.6 β- carotene – – – – – – – – 44
4.6.7 Vitamin C – – – – – – – 44
4.7.1 Tannins – – – – – – 45
4.7.2 Saponins – – – – – – – 45
4.7.3 Polyphenols and flavonoids – – – – – – 45
4.8.1 Phytate, oxalate and haemagglutinin – – – – 46
4.9.1 Colour – – – – – – — – 47
4.9.2 Taste – – – – – – – – 47
4.9.3 Consistency – – – – – – – 47
4.9.4 General acceptability – – – – – – 47
CHAPTER FIVE: DISCUSSIONS,
CONCLUSION AND RECOMMENDATIONS -48
5.1.2 Cowpea leaves and husks samples- – – – 48
5.1.3 Cowpea leaves and husks soup – – – – 51
5.1 Conclusion – – – – – – – 52
5.2 Recommendation – – – – – – 52
REFERENCES – – – – – – – 53
APPENDIX – – – – – — – – – 58
The study examined the chemical
composition of fresh, sundried tender leaves and husks of cowpea ‘Adengee’ (Vigna unguiculata) and organoleptic attributes of their traditional
soups. Information on processing, preparation and utilization of soup meals
based on cowpea leaves and husks were obtained during the focus group
discussion. The tender leaves and husks were parboiled and sundried. Proximate,
micronutrients, phytochemicals and antinutrient levels were determined using
standard procedures. The soups based on fresh and sundried leaves and husks
were analysed prior to sensory evaluation. The data collected were statistically
analysed using means, standard deviation and standard error. All values were
based on residual moisture. Protein for dried leaves was higher (p<0.05)
(39.24 vs. 21.98 and 13.95%) than those of fresh leaves and dried husks. Dried
leaves and husks had lower fat than the control (1.31 and 0.75 vs. 9.10%)
(p<0.05). Sun drying increased ash in both dried leaves and husks (14.74 and
10.86 vs. 4.82%). The lower value for fibre in the dry samples was rather
surprising (14.20 and 20.42 vs.25.13%) (p<0.05). Carbohydrate significantly
increased more in dried husks than in dried leaves. (53.76 Vs. 30.22%)
(p<0.05).The micronutrients in both dried leaves and husks were reduced due
to their volatile nature. Tannins, saponins, flavonoids and polyphenols
decreased significantly (p<0.05) in processed samples due to drying. Soups
based on dried leaves (DS) had higher protein (p<0.05) relative to the soup
based on dried husks (HS) and fresh leaves (FS) (34.40 vs.34.10 and 33.30%).
Similarly, husks based soups had higher fat (34.10 vs.34.05 and
31.44%)(p<0.05) Ash was higher in dried leaves based soup(7.83%) and fresh
leaves soup (7.20%). Fibre for the husks based soup was higher (p<0.05)
relative to fresh and dried leaves based
soups (6.13 vs.5.58 and 6.11%, respectively). The carbohydrate levels were
generally appreciable. All soups had appreciable levels of calcium, phosphorus
and iron. These minerals varied significantly amongst the soups (p<0.05).
Zinc and iodine also differed (p<0.05).β-carotene content of soup based on
fresh leaves was higher (p<0.05) relative to those based on dried leaves and
husks (6.08 vs.5.07 and 5.46RE).Vitamin C varied significantly (0.90 to 1.10mg)
in soups based on fresh leaves and dried husks. Tannins, saponins, polyphenols
and flavonoids in soups based on fresh leaves and dried husks were comparable.
Anti nutrients levels in all soups were generally low. Scores for all
organoleptic attributes of the three soups were more than half (6.17 to 7.70)
of the 9-point scale. The soups were generally acceptable. As judged by the
results, cowpea leaves, husks and their soups have high nutrient potentials to
justify its cultivation, consumption promotion and diversification. Consumption
related information such as nutritional properties should be packaged and
extensively promoted to broaden the knowledge of health and nutritional
benefits of consuming cowpea leaves and husks. The results demonstrate that,
there is a potential in developing multi-purpose varieties with good
performance, which are well-yielding in both leaves and seeds. Therefore,
production related information, such as variety, yields and cultivation
practices as well as processing should be packaged and made available to
extension personnel and governmental agricultural research institutes that
often have a good outreach to farmers.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the study
The scarcity of
documented information on the nutrient potentials of most of the foods consumed
in Nigeria
has greatly contributed towards the ineffectiveness of nutrition education
programmes to meet the nutrient needs of a vast segment of the Nigerian
population. This lack of documented nutrition information has precipitated wrong
choices of foods, low nutrients intake and delay in embracing food
diversification. The knowledge of the influence of processing on the chemical
composition of foods is also necessary for optimizing nutrient reiteration
during handling and processing of our local food materials (Ibok,Ellis &
Owusu,2008).
Recently,
researchers have become convinced that nutrients found in fruits and vegetables
do more than just prevent diseases such as beriberi or rickets. The most
publicized finding reveals that certain vitamins or vitamin precursors, notably
vitamin C; beta-carotene as well as
polyphenols are powerful antioxidants (Consumer Report on Health, 1998).
Antioxidants prevent molecular damage caused by oxidation in that, the
protection offered may fend off many diseases and muscular degeneration (Islam et al., 2002).
Cowpea (Vigna unguiculata L. Walp), an annual herbaceous legume originated in Africa and is wildly grown. Drought tolerance; short growing period and its multi-purpose use make cowpea a very attractive crop to farmers who cultivate in marginal, drought-prone areas with low rainfall and less developed irrigation systems where infrastructure, food security and diminishing malnutrition are major challenges (Hallensleben, Polrech, Heller &, Maass, 2009). Lawrence and Whitbread (2006) described cowpea as one of the most important tropical dual-purpose legumes, being used as leafy vegetable, grain, as fresh cut-and-carry foliage, and for hay and silage.
Cowpea has much
variability within the species. The specie under study is local specie with
coiled pods (Adengee in Tiv,). The
fresh seeds are greenish but golden brown when dried and relatively small in
size compared with the common black eyed beans. This crop can be used at all
stages of growth as a vegetable crop. The tender green leaves are an important
food source in Tiv communities in Benue
State. The green leaves serve
as an ingredient in egusi (melon) soup just like spinach is used in egusi soup;
or the leaves are blanched and sun dried for with egusi soups all year round.
The immature pods are boiled, the boiled seeds are eaten as vegetable and the
husks are sun dried, prepared as egusi soup.
1.2 Statement of the problem
Cowpea leaves and husks have not received the needed research-based attention in Nigeria. Despite the abundance of this vegetable crop in the Nigerian communities, particularly in Tiv land, information on their processing for preservation, uses in preparation of traditional soups and their nutrient composition is scanty in Nigeria literature. Although lately, some researches were carried out on African indigenous vegetables, especially leafy ones, cowpea research continued to focus on improvement of the grain and/or the entire herbage for animal feed (Singh, Ajeigbe, Tarawali, Fernandez-rivera & Musa, 2003). According to Hallensleben et al. (2009), cowpea is an important food legume and its use as a leafy vegetable is essential. Utilization of cowpea as a leafy vegetable and grain crop may provide nutritional and harvest versatility not available with purely vegetable crops such lettuce or monocarpic crops such as wheat (Bubenheim, Mitchell and Nielson,1990). The populace unaware of the high nutrient potentials of this vegetable grows cowpea, wait for the harvest of the matured dry seeds, and discard the leaves. However, it is the leaves of some legumes, including cowpea, that showed much promise for providing part of the vastly increased supplies of nutrients that the world population needs(Bubenheim, Mitchell and Nielson,1990). The need remains to further intensively research on these vegetable and their health benefits. It is, therefore, imperative to elucidate information on the effect of processing on the chemical composition of these cowpea leaves and husks and their soups.
Most Nigerian diets are based on starchy roots, tubers and cereals pounded to produce paste or dried and ground to get fine flour. The flour is stirred with hot water to produce paste. These are consumed with the soups as accompaniment. Nigeria uses food composition tables from American and European countries to calculate nutrient needs of patients in hospitals or public health settings. The information on the processing, preparation, recipe and nutrient content of this local specie of Vigna unguiculata (Adengee) will be very useful in this regard.
1.3 Objectives of the study
1.3.1 General
objective
This study
focused on the food potentials of fresh and processed tender cowpea leaves,
husks and organoleptic attributes of their traditional soup meals.
1.3.2 Specific
Objectives
The specific
objectives of this study were to:
i. collect
information on processing, preparation and utilization of cowpea leaves and
husks in soup meals;
ii. process
cowpea leaves and husks using parboiling and sun drying;
iii. determine
chemical composition of both the fresh and processed leaves and husks;
iv. prepare
soups with these samples and determine their nutrient composition; and
v. assess the
organoleptic attributes of the soups and their accompaniment (pounded yam).
1.4
Significance of the Study.
The result from this study would provide base-line data for compiling nutrient content of Nigerian foods and dishes in the food composition table. This would provide for dietitians an easy tool to calculate nutrient needs for patients in hospitals and clinics. The information from this work would also enable public health nutritionists and dietitians to know how best to use these soups for improvement of feeding habits and diversify diets. This information would assist plant breeders in targeting attributes and characteristics of this cowpea specie for improvement. It would support the identification of traits of local importance, which are crucial for site- specific / local breeding approaches by the public sector both within National Agricultural Research Systems (NARS) and international research institutions.
CHAPTER TWO
2.0 REVIEW
OF RELATED LITERATURE
2.1 Legumes.
Grain legumes
occupy an important place in human nutrition, especially in the dietary pattern
of low-income group of people in developing countries. Legumes are plants of
the beans and pea family. They are rich in protein as compared with other plant
foods (Asanke, Adu-dapaah & Acheampong,2010 ). Legumes, considered as poor
man’s meat are generally good sources of carbohydrates that are released slowly
(Mbah, 2000).
Tharanathan and
Mahadevamma (2005) reported that, legumes are normally consumed after
processing. This, not only improves palatability of foods but also increases
the bioavailability of nutrients, by inactivating trypsin, growth inhibitors
and haemaglutinins. Starch is the major biopolymetric constituent of
legumes. Processing partially modifies
the resistant starch (RS). The latter, is a man made functional dietary fibre,
a unique ingredient that can yield high faecal bulk and butyrate production.
These are the putative markers of colonic health of humans (Tharanathan &
Mahadevamma, 2005). The slow and reduced digestibility of legume starch has
been attributed to its amylose, which is considerably branched and has high
molecular weight (Barret,1990).
Dietary fibre is
a heterogeneous mixture of several types of polysaccharides. Polysaccharide
content is high in legumes, especially the husk fraction. It is beneficial
because it has therapeutic effects on health (Barret, 1990).
2.2 Cowpea
Cowpea (Vigna unguiculata L.Walp) is an annual
legume commonly referred to a black eyed pea, crowder pea, lubia and southern
pea. It originated in Africa, and is widely grown (Davis et al., 1971). There are three basic subgroups of cowpea; the
common cowpea, the catjang and the yard-long bean (Larkin, 2002).
Cowpea has many
cultivars. Each is popular in the localities it is produced. For example
Potiskum, Kabanji, Gauzua, Alouka, Kano white, Maiduguri brown and Ife brown. It
is found in various parts of Nigeria (Ihekeronye & Ngoddy,1985). The
cultivar under study is a local specie that is prostrate (trailing) with coiled
pods referred to as Adengee in Tiv
and Oraludi in Igbo. The fresh seeds
are green and golden brown when dried. The dried seeds are relatively small in
size as compared to the common beans.
Cowpea is
warm-season, annual, herbaceous legume well adapted to many areas of the humid
tropics and temperate zone. The plant tolerates drought, performs well in a
wide variety of soils. Cowpea replenishes low fertility soils when the roots
are left to decay (Uguru, 1996; Hartmann, 2010)
Hallensleben et al. (2009) reported that, cowpea is an important food legume and its use as a leafy vegetable is essential in many African countries. Drought tolerance, short growing period and its multi purpose use make cowpea a very attractive alternative for farmers who cultivate in marginal, drought-prone areas with low rainfall and less developed irrigation systems where infrastructure, food security and diminishing malnutrition are major challenges. This confirms the view of Cheya and Eyzaguirre(1999) who reported that, the multi –purpose use of cowpea has a unique advantage within the African farming systems.
CHEMICAL COMPOSITION OF PROCESSED TENDER LEAVES AND HUSKS OF COWPEA AND ORGANOLEPTIC ATTRIBUTES OF THEIR SOUPS AS CONSUMED IN TIV COMMUNITIES, BENUE STATE, NIGERIA
