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Product Code: 00007579

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The aim of this study was to determine the chemical composition of three vegetables (Telfairia occidentalis, Gnetum africanum and Vernonia amygdalina leaves in their fresh and dried states) and the acceptability of soups made with these vegetables through sensory evaluation. The vegetables were washed and processed as traditionally consumed. They were sundried for 3 days and were used for preparing egusi soup and served with garri for the sensory evaluation. Seventy- five gram (75g) of each of the vegetables was used for soup preparation both in the dried and fresh states.  Some portion of the vegetables both in fresh and dried states were immediately taken to the laboratory for chemical analysis which was done using standard analytical methods. Drying increased the proximate composition (Protein, Ash, Crude fiber, Carbohydrate) of the vegetables. The ash content was higher in dried bitter leaves (7.62%) than in fresh bitter leaves (2.38%) and higher in dried pumpkin leaves (8.47%) than in the fresh pumpkin leaves (4.83%). The protein content was higher in dried ukazi leaves (17.53%) than in the fresh ukazi, higher in dried pumpkin leaves (16.29%) than in the fresh vegetable and higher in dried bitter leaves (19.61%) than in the fresh bitter leaves. Crude fiber was higher in dried ukazi leaves (15.82%) than in the fresh ukazi leaves, it was higher in dried pumpkin leaves (15.53%) than in the fresh pumpkin leaves and higher in dried bitter leaves (15.19%) than in fresh bitter leaves. Drying increased the mineral content of the vegetables while it reduced the vitamin content of the vegetables. Based on the sensory evaluation, the panelists preferred dried ukazi leaves and fresh pumpkin leaves to other samples of the vegetables. The anti-nutrient values were high in the fresh vegetables than in the dried vegetables, the value of alkaloid in fresh (Telfairia occidentalis) leaves was (0.24mg/100g) and in dried (Telfairia occidentalis leaves) the value was (0.01mg/100g). For the fresh leaves of Gnetum africanum, the value for alkaloid was (0.09mg/100g), while the value for dried Gnetum africanum leaves was (0.08mg/100g). The fresh Vernonia amygdalina leaves had alkaloid values of (0.13mg/100g), while the dried Vernonia amygdalina leaves value (0.08mg/100g). Drying as a processing method, could be used to increase the shelf life of vegetables as well as to increase the nutritive value of vegetables.


Title Page




Table of Contents  

List of Tables

List of Figures 


CHAPTER 1:  INTRODUCTION               

1.1          Statement of the Problem                                                                                           2

1.2          Objective of the Study                                                                                               3

1.2.1        Specific objectives                                                                                                     3

1.3          Significance of the Study                                                                                           3


2.1.1       Composition and structure of Vegetables                                                               5                                                                                             

2.2          Nutritional value of Vegetables                                                                               6

2.2.1       Energy content of Vegetables                                                                                 6                                       

2.2.2       Protein content of Vegetables                                                                                 6 

2.2.3       Mineral content of Vegetables                                                                                7

2.2.4       Vitamin content of Vegetables                                                                                7                                                                                                  

2.2.5       Moisture content of Vegetables                                                                              7                                                                                             

2.3          Importance of Vegetables in the Diet                                                                     8                                                                                                         

2.4          Types of Vegetables                                                                                                9                                           

2.4.1       Green leafy Vegetables                                                                                           10                           

2.5        Post Harvest Handling of Vegetables                                                                     10                                                                               

2.5.1     Preservation and storage of green leafy vegetables                                              11                                                                                                             

2.5.2     Different methods used for preserving and storing green leafy Vegetables           12                                                                                                            

2.6        Different Methods Used in Processing Vegetables                                                14                  

2.7        Blanching Process                                                                                                   14                                                     

2.7.1     Hot water blanching                                                                                                15                                                                                      

2.7.2     Steam blanching                                                                                                      15                                                       

2.8        Drying Process                                                                                                        16                                                

2.8.1     Sun and shade drying                                                                                             17                                                       

2.8.2     Oven drying                                                                                                            18                                                                                

2.8.3     Solar drying                                                                                                            18                                                                                                           

2.8.4     Microwave and cabinet drying                                                                               19

2.9        Effects of Processing on Vegetables                                                                      19

2.10      Effects of Drying on the Nutrient and Sensory Properties of Vegetables             20                                                                              

2.10.1   Effect of drying on nutrients                                                                                  20

2.10.2   Effects of drying on sensory quality of vegetables                                                21

2.11      Description of Bitter Leaf (Vernonia amygdalina)                                                21

2.11.1   Major uses and functions of bitter leaf                                                                  21

2.11.2   Chemical properties of Vernonia amygdalina                                                       22

2.11.3   Uses of Vernonia amygdalina                                                                               22                   

2.12      Origin of Telfairia occidentalis                                                                              22

2.12.1   Chemical properties of Telfairia occidentalis                                                        23

2.12.2   Uses of Telfairia occidentalis                                                                                23

2.13      Gnetum africanum (Ukazi)                                                                                   23

2.13.1    Chemical properties of Gnetum africanum                                                          24

2.13.2  Uses of Gnetum africanum                                                                               24

CHAPTER 3:     MATERIALS AND METHODS                                                 25

3.1       Experimental Design                                                                                         25

3.2       Sample Collection                                                                                             25                                                                                            

3.3       Sample Preparation                                                                                           25                                                                                                

3.3.1    Flow chart for processing of fresh vegetables                                                  26                                                                                             

3.3.2    Flow chart for processing of dried vegetables                                                  27                                                                        

3.4       Soup Preparation                        27                        

3.4.1    Recipe for egusi soup                                                                                        28                                                                                       

3.4.2    Method of preparing egusi soup using pumpkin leaves                                    29                                          

3.4.3    Method of preparing egusi soup using bitter leaves                                          29                                                                                                            

3.4.4    Method of preparing egusi soup using ukazi leaves                                          30                                                        

3.5       Packaging and Storage of Samples                                                                    30                    

3.6       Chemical Analysis                                                                                             30                                                                                          

3.6.1     Proximate composition                                                                                     30                                                                   Determination of moisture content                                                                   31                                                         Determination of fat content                                                                            32                   Determination of ash content                                                                           32                                                                            Determination of protein content                                                                     33               Determination of carbohydrate content                                                           34  Determination of crude fiber content                                                               34        

3.6.2     Mineral analysis                                                                                                35                                                                  Determination of zinc, iron and magnesium contents                                      35                                                                    Determination of Potassium and Sodium Contents                                         35         

3.6.3     Vitamin analysis                                                                                               36                                            Determination of vitamin C content                                                               36             Determination of niacin content                                                                     38                                                             Determination of riboflavin content                                                               38                                                              Determination of thiamine content                                                                 39  

3.6.4      Antinutrient analysis                                                                                       40                                                     Alkaloid determination                                                                                   40   Flavonoid determination                                                                                 41                                                                               Determination of tannin and oxalate                                                              41     

3.7         Sensory Evaluation                                                                                         42                  

3.8         Statistical Analysis                                                                                         43


4.1         Proximate Composition of Fresh and Dried Vegetables                               44   

4.2         Vitamin Composition of Fresh and Dried Vegetables                                  48   

4.3         Mineral Composition of Fresh and Dried Vegetables                                  51      

4.4         Phytochemical Composition of Fresh and Dried Vegetables                       53

4.5         Sensory Attributes of fresh and Dried Vegetables                                       55                                                                                                               


5.1         Conclusion                                                                                  57

5.2          Recommendations                                                                                       57

References                                                                                                                 58




Table                                                                                                             Page

3.4.1     Recipe for egusi soup                                                                       28 

4.1        Proximate composition of fresh and dried vegetables                     45      4.2        Vitamin composition of fresh and dried vegetables                        49                                                                                                                                                                                 4.3        Mineral composition of fresh and dried vegetables                         53     4.4        Phytochemical composition of fresh and dried vegetables              54                                                      4.5        Sensory attributes of soups prepared with fresh

             and dried vegetables                                                                         56                                                                                                 




Figure   3. 3.1:  Flow chart for processing of fresh vegetables                     26

Figure   3. 3.2:  Flow chart for processing of dried vegetables                     27











Vegetables serve as indispensable constituents of human diet, supplying the body with minerals, vitamins, protein and energy, and as addition to certain hormone precursors (Fasuyi, 2006). In Nigeria, as in other tropical countries of Africa where the daily diets are dominated by starchy foods, vegetables are said to be cheapest and most readily available sources of important nutrients (David, 2002). They are important low cost foods containing low levels of fat and high levels of vitamins, minerals, fiber, some calorie and protein (Mepba et al., 2007). Vegetables are also good sources of carotenes, ascorbic acid, riboflavin, folic acid and minerals like calcium, iron and phosphorus which have several health benefits including therapeutic uses such as treatment of scurvy, prevention of cold, correction of hypertyrosinemia, malformation of bones and anaemia in new born infants ( Fasuji, 2006).

Chemicals in plant are referred to as phytochemicals. They are naturally occurring components in fruits and vegetables. They give plants their color, flavor, smell and are part of the plant natural defense system (disease resistance). According to Liu (2004), their medical values are based on some phytochemical substances that they contain, which produce definite physiological actions in the human body. The most important of these bioactive constituents of vegetables are alkaloids, tannins, flavonoid and phenolic compounds (Edeoga et al., 2005).

Vegetables are eaten raw or processed, thus any methods selected for processing vegetables should be such that does not adversely affect the color, texture, flavor and nutritional values especially the vitamins and minerals (Edeoga et al., 2006). Fasuyi (2006) reported that consumption of vegetables helps toward controlling blood pressure and cholesterol levels, prevent some types of cancer, avoid painful intestinal ailment called diverticulosis and guard against cataract and muscular degeneration which are two common causes of vision loss.

The organoleptic properties of vegetables are due to the composition of the pigment that they contain. Vegetables contain non-volatile acids such as malice, citric, oxalic and succinct acid which contribute to their flavor. The color of vegetables depends on the pigment they contain anthocyanin impart blue, purple and red color to vegetables such as ripe tomatoes and red cabbage; carotenoids are responsible for yellow color of carrots, sweet potatoes and maize (Oluwole et al., 2003). Chlorophyll gives vegetables green color especially leafy ones, green peas and cucumber.

There are some leafy vegetables that are grown and used in Abia State, whose chemical and anti–nutrient properties were studied in this work. They are ‘Ukazi’   (Gnetum africanum), ‘Ugu’ (Telfairia occidentalis) and ‘Olugbu’ (Vernonia amygdalina).


1.1   Statement of the problem

Micronutrient deficiency (hidden hunger) still remains a public health problem in Nigeria despite the level of efforts made to reduce it. World health organization  (WHO, 2002) reported that about 30% of the population in developing countries suffer from one or more of the multiple forms of nutritional deficiencies, especially that of micronutrients. Although some vegetables are scarce and expensive during dry season, during rainy season  some people do not still make use of most vegetables, thus micronutrient deficiency is still high, (Chubike, 2013). These three vegetables are; ‘Ukazi’ (Gnetum africanum), ‘Ugu’ (Telfairia occidentalis) and ‘Olugbu’ (Vernonia amygdalina), are mostly consumed in the eastern part of Nigeria. These vegetables are also often dried and sent to Nigerians living abroad too, since they still enjoy Nigerian dishes in foreign lands. This study aimed at determining the chemical and organoleptic attributes in both fresh and dried states.


The general objective of this study was to determine the chemical and organoleptic attributes of Gnetum africanum, Telfairia occidentalis and Vernonia amygdalina in their fresh and dried states. 


The specific objectives were to:

 1.  determine the chemical content of these vegetables by assessing their proximate, minerals, vitamins and anti-nutrient composition.

 2.   assess the acceptability of soups made with these vegetables using sensory evaluation.

1.3   Significance of the study

1. The result obtained in this work could provide data on the nutrient content, especially micronutrient content of the selected vegetables consumed in Abia State.

2. Health professionals and other vegetable users (vegetarians) can select vegetables based on the information provided. It could also enable the agriculturists to cultivate different vegetables. It could serve as a guide for individuals, families and even communities to select healthy vegetables for consumption.

3. The information from the chemical content of these vegetables can form part of food composition table which can be used by other researchers.


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