ABSTRACT
Cookies are nutrient dense food products consumed mostly in-between meals by both children and adults. They are usually made from wheat grains which is not cultivated in tropical countries like Nigeria due to unfavourable climatic conditions. Chemical and sensory properties of cookies from blends of sorghum, orange-fleshed sweet potato and date pulp were investigated. Cookies were produced from flour blends (100:0:0, 70:20:10, 65:25:10, 50:40:10, 55:35:10) of sorghum, orange-fleshed sweet potato and date pulp, respectively. Cookies made with 100% sorghum flour served as the control. Proximate composition, mineral, vitamin and antinutrient content, as well as sensory properties of the cookies were evaluated using standard analytical procedures. Data generated were statistically analysed by one way analysis of variance using Statistical Product for Service Solution version 23.0. The proximate composition revealed that the moisture content (9.58 to 10.27 %), crude protein (5.96 to 7.01 %), fat (8.16 to 8.65 %), dietary fibre (2.48 to 3.01 %), ash (1.40 to 1.92 %), carbohydrate (70.33 to 71.56 %), and energy value (1602.57 to 1618.54 KJ) of the cookies. Minerals like phosphorus (2.88 to 4.32 mg/100g), calcium (12.98 to 44.06 mg/100g), sodium (4.03 to 20.18 mg/100g), potassium (3.21 to 32.62 mg/100g), and zinc (4.44 to 4.67 mg/100g) were obtained in the cookies. The cookies possessed pro-vitamin A (63.12 to 351.23 µg/100g), vitamin B1 (2.43 to 4.66 mg/100g), vitamin B2 (0.21 mg to 1.38 mg/100g), vitamin B3 (0.54 to 1.35 mg/100g), and vitamin C (1.22 to 1.73 mg/100g). The antinutrient contents of the cookies showed the presence of phytate (0.05 to 1.17 mg/100g), saponin (0.87 to 1.03 mg/100g), tannin (0.43 to 1.95 mg/100g), and trypsin inhibitor (3.21 to 32.62 mg/100g). The sensory analysis of the cookies revealed that the mean score for appearance ranged from 5.05 to 7.20, whereas 4.40 to 7.50, 3.45 to 7.40, 4.35 to 7.45, and 4.00 to 7.80 was obtained as the mean score for flavour, taste, texture, and general acceptability of the cookies. This study showed that nutrient dense and acceptable cookies can be produced from flour blends of indigenous crops like sorghum, orange-fleshed sweet potato and date pulp.
TABLE OF CONTENTS
TITLE PAGE i
CERTIFICATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
TABLE OF CONTENTS v
LIST OF TABLES viii
LIST OF FIGURES ix
ABSTRACT x
CHAPTER 1
INTRODUCTION 1
1.1 Statement of problems 3
1.2 Objectives of the study 5
1.3 Significance of the study 5
CHAPTER 2
LITERATURE REVIEW 7
2.1 Relevance of cereals in human nutrition 7
2.2 Overview of sorghum 8
2.2.1 Nutritional and health benefits of sorghum 9
2.2.2 Processing and food uses of sorghum 11
2.2.3 Antinutritional factors in sorghum and effect of processing
on their reduction 13
2.3 Overview of sweet potato 14
2.3.1 Nutritional value and health benefits of orange fleshed sweet potato 15
2.3.2 Processing and utilization of orange fleshed sweet potato 17
2.3.3 Anti-nutritional factors in orange fleshed sweet potato 20
2.4 Sugar and its detrimental effect on human health 21
2.5 Potentials of date fruit as a sugar substitute 22
2.6 Composite flour 23
2.7 Overview of cookies 25
2.7.1 Functions of ingredients used in cookies production 28
CHAPTER 3
MATERIALS AND METHODS 30
3.1 Study design 30
3.2 Raw materials collections 30
3.3 Sample preparation 30
3.3.1 Production of orange-fleshed sweet potato flour 30
3.3.2 Production of sorghum flour 33
3.3.3 Preparation of date palm pulp flour 35
3.3.4 Formulation of composite flour 37
3.3.5 Production of cookies 38
3.4 Packaging and storage of samples 40
3.5 Chemical analysis 40
3.5.1 Proximate composition 40
3.5.1.1 Determination of moisture content 40
3.5.1.2 Determination of ash content 40
3.5.1.3 Determination of fat content 41
3.5.1.4 Determination of dietary fibre 42
3.5.1.5 Determination of crude protein 42
3.5.1.6 Determination of carbohydrate content 43
3.5.1.7 Determination of energy value 43
3.5.2 Mineral analysis 44
3.5.2.1 Determination of phosphorus 44
3.5.2.2 Determination of calcium and magnesium 44
3.5.2.3 Determination of potassium 46
3.5.2.4 Determination of zinc 46
3.5.3 Vitamin analysis 47
3.5.3.1 Determination of β-carotene 47
3.5.3.2 Determination of vitamin B1 (thiamin) 48
3.5.3.3 Determination of vitamin B2 (Riboflavin) 48
3.5.3.4 Determination of vitamin B3 (Niacin) 49
3.5.3.5 Determination of vitamin C (Ascorbic acid) 50
3.6 Antinutrient analysis 51
3.6.1 Determination of phytate 51
3.6.2 Determination of saponin 51
3.6.3 Determination of trypsin inhibitor 52
3.6.4 Determination of tannin 53
3.7 Sensory evaluation 54
3.8 Statistical analysis 55
CHAPTER 4
RESULTS AND DISCUSSIONS 56
4.1 Proximate composition of cookies produced from
flour blends of sorghum, orange-fleshed sweet potato and date palm 56
4.2 Mineral contents of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 63
4.3 Vitamin contents of cookies produced from flour blends
of sorghum, orange-fleshed sweet potato and date palm 68
4.4 Antinutrient contents of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 73
4.5 Sensory properties of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 78
CHAPTER 5
CONCLUSION AND RECOMMENDATIONS 84
5.1 Conclusion 84
5.2 Recommendations 85
References 87
Appendix 104
LIST OF TABLES
Table 3.1: Flour blends formulation 37
Table 3.2: Recipe for production of cookies 38
Table 4.1: Proximate composition of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 57
Table 4.2: Mineral contents of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date fruit 64
Table 4.3: Vitamin contents of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 69
Table 4.4: Antinutrient contents of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 75
Table 4.5: Sensory properties of cookies produced from flour blends of sorghum, orange-fleshed sweet potato and date palm 79
LIST OF FIGURES
Figure 3.1: Flow chart for the production of orange-fleshed sweet potato flour 32
Figure 3.2: Flow chart for the production of sorghum flour 34
Figure 3.3: Flow chart for the production of date palm pulp flour 36
Figure 3.4: Flow chart for cookies production 39
CHAPTER 1
INTRODUCTION
Cookies are popular confectionery products with a unique texture and taste, long shelf-life and a relatively cheap price (Petrovic et al., 2016). They are nutritive snack produced from single or composite dough that is transformed into digestible and more appetizing products through the action of heat in the oven (Adeyeye, 2016). Cookies are consumed extensively all over the world as a snack food and on a larger scale in developing countries (Peter et al., 2017). They are mainly produced with ingredients such as flour, fat, water and sugar; while salt, milk, leavening agent, and other ingredients that can aid in meeting specific nutritional or therapeutic needs of consumers can also be used (Abayomi et al., 2013; Ajibola et al., 2015). Sugar, one of the major ingredients for cookies production contains high calories with no essential nutrients, thus, causing metabolic problems such as type II diabetes, obesity and so on (Peter et al., 2017). Substitution of sugar with date fruit pulp in bakery products has been advocated for as a means of curbing the afore-stated health related issues (Peter et al., 2017).
Date palm fruit (Phoenix dactylifera) is a sweet edible fruit from the family of Arecaceae (Al-daihan and Bhat, 2012). The fruit is a drupe in which an outer fleshy part consists of pulp and pericarp surrounding a shell of hard endocarp with a seed inside (Farheena et al., 2015). Date fruit is rich in fibre (Hamza et al., 2014), antioxidant and flavonoids such as beta-carotene, lutein and zeaxanthin (Dada et al., 2012). They are excellent source of iron, calcium, copper, magnesium, potassium, and minor source of vitamins A, and B2 (Dada et al., 2012; Farheena et al., 2015). These make them to have high potential to be used as functional food (Ghinimi et al., 2017). Pulp of date palm is a rich source of beta-carotene, lutein, zeaxanthin (Farheena et al., 2015), fructose and glucose (Dada et al., 2012), thus making it an ideal replacement for sugar (sucrose) in cookies production (Hamza et al., 2014). Cookies can be produced with flours from local staples so far as they are readily available and provide increased nutritional potential.
Orange-fleshed sweet potato (Ipomoea batatas) is among the sweet potato varieties being promoted in Nigeria as a food-based measure to improve dietary intake of vitamin A (Owade et al., 2018). Most varieties of orange-fleshed sweet potato contains 3000 to 16000 µg/1000 g of β-carotene and this contributes to 250 to 1300 µg/100 gretinol activity equivalents (RAE) (Gurmu et al., 2014). Orange-fleshed sweet potato is also made up of 2.03 to 4.19 g protein, 14.46 to 22.86 g fat, 153.63 kcal energy value (Omodamiro et al., 2013; Sanoussi et al., 2016), iron, zinc, calcium and magnesium (Gurmu et al., 2014). It can be used as food in their fresh form after cooking or processed into flour which can be used as a raw material in cookies, bread, cake and extruded snack production.
Sorghum (Sorghum bicolor (L) Moench) is a member of grass family. Globally, it is the fifth most important cereal crop by acreage after wheat, rice, maize and barley (Dahir et al., 2015). Sorghum is often referred to as poor people crop as it can sustain the lives of the poorest rural people (Felix et al., 2015). Its grain has a lot of nutritional benefits due to its rich antioxidant properties (Adegbola et al., 2013). Sorghum grains contain 325 of calories, 10.8 mg of protein, 0 mg of sugar, 3.1 mg of fat, 6.0 mg of fibre and 0 mg of cholesterol. They are also rich in vitamins and minerals such as vitamin B1, B2 and B3, calcium, potassium, iron, phosphorus and sodium (Adegbola et al., 2013). Its consumption reduces the risk of certain types of cancer in humans (Yang et al., 2009). Owning to the nutritional and health benefits of sorghum, it is increasingly becoming the basis for successful food formulations in Nigeria (Obiakor-Okeke et al., 2014; Adeyeye, 2016; Okoth et al., 2017).
The use of composite flours in the production of cookies and other baked products has become common in many parts of the world. Therefore, this experimental research is designed to produce cookies using composite flours from blends of sorghum, orange-fleshed sweet potato and date palm pulp.
1.1 STATEMENT OF PROBLEMS
The increasing urbanization coupled with growing number of working mothers have profoundly contributed to the popularity and increased consumption of cookies. Wheat flour, the main ingredient for cookies production is mainly imported to Nigeria because of unfavourable climatic conditions for its commercial cultivation. This importation places a considerable burden on the foreign exchange reserve of Nigeria’s economy (Nwanekezi, 2013). More so, in processing of cookies, sucrose is the most commonly used sweetening agent. However, sucrose has its own problem of causing metabolic problems which includes but not limited to type II diabetes, obesity and so on (Peter et al., 2017). Aside this, Nigeria spends most of its foreign exchange on importation of sugar. This depletes the country’s foreign exchange reserve (Nwanekezi et al., 2015).
Vitamin A deficiency is a major public health concern of the developing countries and is responsible for blindness, retarded growth and death among young children (Ukom et al., 2016). Animal foods such as liver, egg and butter which are good sources of vitamin A are not affordable by average families. This made researchers to advocate for consumption of inexpensive plant foods which although do not contain vitamin A as such but do contain its precursor, β-carotene that can be converted to vitamin A by the human body. Orange-fleshed sweet potato which is well known to be an excellent source of β-carotene and can contribute to increase intake of β-carotene thereby combating the afore-stated health effect is underutilized (Sanoussi et al., 2016).
Despite the nutritional advantages of sorghum and its potential for economic enhancement, relatively little research attention has been devoted to its utilization in food systems (Dahir et al., 2015).
In Nigeria, prevalence of iron (45 %), zinc (43.3 %) and vitamin A (51.1 %)deficiency in children is well documented (Abubakar et al., 2017; Ayogu et al., 2018), while 40 % of adolescents are reported to be deficient in iron, vitamin A (Ayogu et al., 2016); with prevalence of their zinc deficiency being 20 % (National Nutrition and Health Survey, 2018). More so, 2.52 % of children in Lagos State have type 1 diabetes (Oyenusi et al., 2016). Due to the problems identified, it is important to carry out the research.
1.2 OBJECTIVES OF THE STUDY
The general objective of this study was to produce and evaluate the chemical and sensory properties of cookies from blends of sorghum, orange-fleshed sweet potato and date pulp.
The specific objectives of the study were to:
i. Produce composite flour from sorghum, orange-fleshed sweet potato and date pulp.
ii. Produce cookies from the composite flour blends.
iii. Determine the proximate compositions of the cookies.
iv. Evaluate the mineral contents (phosphorus, calcium, magnesium, potassium and zinc) of the cookies.
v. Analyse the vitamin contents (β-carotene, thiamin, riboflavin, niacin, ascorbic acid) of the cookies.
vi. Determine the antinutrient contents (phytate, saponin, trypsin inhibitor and tannin) of the cookies.
vii. Determine the sensory attributes of the cookies.
1.3 SIGNIFICANCE OF THE STUDY
Findings from this study will contribute in effective dietary guidance in developing countries such as Nigeria. Substitution of sugar with date fruit pulp in production of cookies remains the most practicable option to drastically reduce consumption of sugar in Nigeria. Cookies produced in this study will increase the use of date fruit in bakery products, reduce lots of money Nigeria spend on importation of sugar and also protect consumers of the cookies from being victims of metabolic problems such as diabetes. This will also save the Nation’s foreign exchange, create a novel food product, increase the demand of orange fleshed sweet potato and sorghum for food; and thus, prevent them from going into extinction.
Cookies produced in this study will be highly valuable in the management of malnutrition or hidden hunger like vitamin A, iron and zinc deficiency in children and adolescents. This study will also reveal appropriate method of processing nutrient dense and economic cookies from blends of local staples such as orange-fleshed sweet potato, sorghum and date fruit pulp.
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