ABSTRACT
Available synthetic colour additives used in food have been shown to exhibit genotoxic effects and pose several potential health hazards to human. Hence, the global increase in the demands for natural colour additives. This study therefore investigated the quality and stability of ethanolic extracts from Capsicum annuum for use as food colourants. Colour pigments and other constituents were extracted from bell pepper (var. conoides miller) and sweet pepper (var.longum nigrum) using ethanol. The extracts were subjected to pH adjustment and addition of ascorbic acid as stabilizer under varying conditions of light (white light, UV light and in the dark). The results showed that the extracts maintained their colour at an acidic pH. The yield of colour pigments and other constituents from both varieties were high (above 70%) and they also had good colouring ability as shown by their colour units of 24,460 for bell pepper (var. conoides miller) and 27,645 for sweet pepper (var. longum nigrum). The data from this study suggests that the most suitable condition to maintain stability is in acid media and 0.5% ascorbic acid kept in the dark. Also both extracts had a low energy value, they need to be fortified while being incorporated into food.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Abstract vi
Table of Content vii
List of Figures ix
List of Tables xi
List of Plates xii
List of Appendices xiii
Abbreviations, Glossaries and Symbols xv
Chapter One 1
1.0 Introduction 1
1.1 Food Additives 1
1.2 Statement of Research Problem 4
1.3 Justification 5
1.4 Aim and Objectives 6
1.4.1 Aim 6
1.4.2 Specific Objectives 6
Chapter Two 7
2.0 Literature Review 7
2.1 Historical Background of Food Colour 7
2.2 Classification of Food Colours 8
2.3 Uses of Colour in Food and Drinks 9
2.4 Pepper (Capsicum annuum L) 10
2.4.1 Bell pepper 11
2.4.2 Sweet pepper 12
2.5 Uses of Pepper 15
2.6 Carotenoids 17
2.6.1 Classification of carotenoids 18
2.6.2 Factors influencing carotenoid composition 20
2.6.3 Functions of carotenoids 21
Chapter Three 23
3.0 Materials and Methods 23
3.1 Materials 23
3.1.1 Reagents 23
3.2 Methods 23
3.2.1 Preparation of Reagents 23
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3.3 Collection and Preparation of Pepper Sample 26
3.3.1 Extraction of colour and other constituents 26
3.3.2 Stability Measurements of Extracts 26
3.4 Evaluation of the Nutritional Components of the Extract 27
3.4.1 Determination of total ash 27
3.4.2 Determination of crude fibre 27
3.4.3 Moisture content 28
3.4.4 Total nitrogen 28
3.4.6 Determination of total carbohydrate 29
3.5 Determination of Functional Groups in Extracts using FTIR Spectrometry 29
3.6 Extractable Colour Measurements in ASTA Units 30
3.7 Statistical Analysis 30
Chapter Four 32
4.0 Results 32
4.1 Yield of Extracts 32
4.2 Stability Studies of the Extracts. 32
4.2.1 Bell pepper 32
4.2.2 Sweet pepper 33
4.3 Characteristics of Extracts 41
4.4 Nutritional Components of Extracts 41
Chapter Five 69
5.0 Discussions 69
5.1 Yield of Extracts 69
5.2 Variations in pH against Time 69
5.3 FTIR Spectra of Extracts. 71
5.4 Colour Measurement 73
5.5 Evaluation of Nutritional Components of Extracts. 73
Chapter Six 75
6.0 Conclusions and Recommendations 75
6.1 Conclusion 75
6.2 Recommendations 76
REFERENCES 78
APPENDICES 83
APPENDIX VI 89
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CHAPTER ONE
1.0 INTRODUCTION
1.1 Food Additives
Food additives are substances usually added to foods in small quantities during the process of production, storage and/or packaging in order to improve the appearance, texture, taste, colour, smell, durability, or nutritional value (FI, 2010). In the United States, colours added to foods are referred to as food additives under the 1958 Food, Drug, and Cosmetics Act and are defined as “any dye, pigment or substance which imparts color when added or applied to a food, drug or cosmetic, or to the human body” (USFDCA 2014). Consumers naturally enjoy bright colours in food because, as the saying goes, people “taste” first with their eyes, then their mouths (Chaitanya, 2014; Matulka and Tardy, 2014). Colour is one of the most important sensory qualities as it helps us to accept or reject particular food items. It is used as a measure of the quality and nutrient content of foods (Chaitanya, 2014). Colour is important in consumer perception of food and it is often associated with a specific flavour and intensity of flavour (Abdeldaiem, 2014). People often associate certain colours with certain flavours, and the colour of food can influence the perceived flavour in anything from candy to wine (Jeannine, 2003). It is very unfortunate that most manufacturing process in food processing decreases the inherent colour(s) contained in food. For instance, the simple act of heating can destroy pigment molecules like anthocyanins that provide the attractive bright red and blue shades in fruits and berries (Laleh et al., 2006). Food colour is an additive in the form of any dye, pigment or any substance that is used to give foodstuff a more attractive look or impart colour. They come in numerous forms consisting of liquids, powders, gels and pastes. Some are natural colours, but most are artificial and may have toxic properties (Abdeldaiem, 2014; Eissa et al., 2014). These additives are added to food
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to replace or boost colour lost as a result of processing procedures such as exposure to light, temperature extremes, moisture and storage conditions.
Furthermore, they may be added to correct natural variations in food colour, to minimize batch variations in processing, enhance colours that occur naturally in food or provide colour to colourless and “fun” foods or make food more attractive, appetizing, informative and finally allow consumers to identify products on sight (Barrows et al., 2009; Chaitanya, 2014; Saltmarsh and Insall, 2013). The importance of food colour additives cannot be over emphasized. For instance, without colour additives, colas would not be brown, margarine would not be yellow and mint ice cream would not be green (Katz, 2014). Colour additives are now recognized as an important part of practically all processed foods.
An increasing number of commercial colour additives, which are used as food colourants have been shown to exhibit genotoxic effects (Eissa et al., 2014). Hence, the need for colour additive from natural sources, since the commercially available colour additives possess potential hazards to the human health (Kirti et al., 2014; Chengaiah, et al., 2011). Globally, there is an increasing demand towards the use of natural colour additives in food. Much awareness is created amongst consumers regarding natural products and adopting a more natural way of life. In recent times, it has been observed that people now prefer natural food, herbal medicines, natural curing practices and even organic farming i.e. without using chemical fertilizers and pesticides (Abdeldaiem, 2014; Kirti et al., 2014). This is mostly due to the unbridled use of synthetic chemicals, colours, and derived products that has led to various human health hazards (Eissa et al., 2014). As a result of the high demand of natural colourant in food and drinks, most food industries now replace synthetic colourants in their products with natural pigments (Kirti et al., 2014).
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Natural colourants for food are made from renewable sources. Nature is rich in colours obtained from fruits, vegetables, roots, minerals, plants, microalgae, and so forth, and due to their origin from biological materials they are often called “biocolours” (Pattnaik et al., 1997; Kirti et al., 2014). Most often, the colourants are extracted from plant materials, but other sources such as insects, algae and fungi are used as well (Aberoumand, 2011; Abou- Arab, 2011).
Pepper (Capsicum annuum) is a typical example of a natural source of food colourant. It is used as spices in a broad variety of dishes in Nigeria and the entire world. Pepper belongs to the genus Capsicum with approximately 27 different species and to the Solanaceae family which includes the major types of chilli pepper. There are five domesticated species of pepper: the three most wide-spread are C. annuum, C. frutescens, C. chinense, together with C. pubescens and C. baccatum (Cantrill, 2008). The first to be introduced worldwide was C. annuum, originating from Mexico. It is divided into two categories: sweet (or mild) peppers and hot (or chilli) peppers. They are commonly called Chilli pepper, red or green pepper, or sweet pepper in Britain (Reddy and Sasikala 2013). The large wild form is called bell pepper in the U.S. and Canada (Reddy and Sasilaka 2013). It is called paprika in some other countries. In Nigeria, it is called “ose” in Igbo, “ata” in Yoruba and a host of names depending on the specie such as “tattasai”, “atarugu”, “borkonu” in Hausa.
The fruits of Capsicum annum contain colouring pigments, pungent principles, resins, protein, cellulose, pentosans, mineral elements and very little volatile oil (Cantrill 2008). The paprika species contains dark-red colourful oil liquid, which can be used as a fine food colour with good mobility. This colour pigment is light-resistant, heat-resistant, acid-resistant, and alkali-resistant and will not be affected by metal ion (Reddy and Sasikala 2013). Capsaicin, the spicy chemical in peppers, has also been shown to be a potent anti-inflammatory in vivo (Sancho et al., 2002). In Nigeria, Capsicum annuum is used as a colour additive to give a bright reddish colour to food such as stew, moi-moi and akara made from ground beans and eaten in almost
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every part of the country. The green specie of pepper is used as colourant to flavor foods like fried rice and vegetable salad. The pigments present in paprika are a mixture of carotenoids, in which capsanthin and capsorubin are the main compounds responsible for the red colour of the dye (Chaitanya, 2014; Chengaiah et al., 2010).
As a result of the global increase in the demands for natural colour additives in food, this research therefore aims to extract the colour pigment and other constituents present in Capsicum annuum, as well as determine its quality and stability.
1.2 Statement of Research Problem
There has been a geometric increase in the demand for food colour globally over the last decade (Chaitanya 2014). In year 2000 the demand for food colour in the global market was 2400 metric tonnes and it increased to 3000 metric tonnes by the year 2005 and further to 8000 metric tonnes by the year 2010 and was expected to increase to 15000 metric tonnes by the year 2015 (Chaitanya, 2014).
The investment in natural food colour market worldwide has reached US $ 1 billion and is continuously growing as there is demand for natural food colours against synthetic food colours (Sahar et al., 2012; Ree, 2006). Although there is no documented literature with respect to the demand for food colours in Nigeria, however, it is believed to be on the rise looking at the number of eateries, restaurants and commercial catering services.
Several reports have attributed the cause of cancer and other diseases of mankind to the synthetic chemicals used in food. Most of these chemicals exhibit genotoxic effects (Eissa et al., 2014). The effect on health from the prolonged usage of synthetic and inorganic food colours on the quality of human health calls for urgent attention. Hence, the need for this research.
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1.3 Justification
The advantages of using natural colourants are numerous as they are biodegradable, harmless, unsophisticated and harmonized with nature. They are obtained from renewable sources and their preparation involves a minimum possibility of chemical reactions (Abdeldaiem, 2014; Chengaiah, 2010). By and large, natural colourants do not cause health hazards; on the contrary, they sometimes act as health cures like turmeric and annatto (Abdeldaiem, 2014).
There is a growing need for natural colours to be used in foods, pharmaceuticals, cosmetic products and so on (Aberoumand , 2011; Chengaiah , 2010) Consumers tend to favour a more natural way of life because of health challenges posed by the excessive use of artificial or synthetic colours (Blanc, 2009; Chen and Wu 2009).
The use of natural dyes dates back to 2600 BC in China (Chaitanya, 2014) although archeologists believe the use of food colour dates back to 1500BC (Burrows 2009; McKone 1995). Addition of colourants to foods is reported in Europe during the Bronze Age (Madhava Naidu and Sowbhagya 2012; Chaitanya, 2014). Since 1500 BC, the Egyptian cities candy makers have been known to make use of natural extracts and wine to improve the appearance of food (Madhava Naidu and Sowbhagya 2012; Chaitanya, 2014).
Marketing strategy of food by major manufacturers is greatly influenced by colour (Sharma 2013), since human appetites are greatly influenced and stimulated by colour (Abou-Arab, 2011; Malik et al., 2012). Colour may sometimes discourage eating certain foods and diminish the desire for that food hence over the last 2 to 3 decades many food industries ensure that their food is not only tasty, but visually appealing. This brings out the importance of colour as it relates to food choices (Betina, et al., 2012).
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1.4 Aim and Objectives
1.4.1 Aim
To assess the quality and stability of the ethanol extracts of bell and sweet pepper for application as food colourant
1.4.2 Specific Objectives
The aim will be achieved through the following objectives:
1. Extraction of the colour pigments and their constituents from two varieties of Capsicum annum var. conoides miller (bell pepper) and var.longum nigrum (sweet pepper)
2. Determination of the yield of the extracts.
3. Evaluation of the stability of the extracts.
4. Determination of the functional groups present in the extracts using FTIR.
5. Evaluation of some of the nutritional components of the extracts.
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