Effect of orange peel flour on the quality

Aims: This study was carried out to investigate the effects of orange peel flour (OPF) substitution with wheat flour in bread production (substitution levels of 3, 6 and 9%) on the proximate composition, phytochemicals content, baking and sensory characteristics. Place and Duration of Study: Department of Food Science and Technology, Ebonyi State University, Abakaliki, Ebonyi State, Nigeria for seven months. Methodology: Oranges were washed thoroughly and peeled. Peels were boiled in water, sundried and ground into flour. Bread was produced by replacing wheat flour with 3, 6 and 9% OPF. Bread samples were analyzed for proximate composition (fat, moisture, protein, ash, fibre and carbohydrates), phytochemicals (tannins, saponins and alkaloids), baking characteristics (oven spring, loaf volume, specific volume and weight) and sensory quality. Results: The addition of orange peel flour led to reduction in protein (8.2-2.7%) and fat (1.7-0.8%) but increased the ash (2.3-4.3%), fibre (0.6-5.8%) and carbohydrates (59.962.1%) contents. Phytochemicals levels also increased with increased levels of orange peel flour in the samples. Tannins ranged from 3.6-8.0mg/g, saponins from 0.9-1.4mg/g and alkaloids from 3.6-4.8mg/g. Oven spring decreased from 2.0 to 0.2cm, loaf volume from 8.0 to 4.8cm and specific volume from 5.3 to 3.2cm/g. Sensory quality decreased with increase in orange peel flour for all the attributes studied. However sensory quality of bread made with 3% OPF did not differ from that made with 100% wheat flour. Conclusion: The use of orange peel flour in bread has the advantage of improving the Original Research Article British Journal of Applied Science & Technology, 4(5): 823-830, 2014 824 fibre, ash and phytochemicals levels in bread. However only bread produced with 3% OPF had sensory quality comparable to that produced with 100% wheat. Orange peel flour in bread production will not only add value to food but will also reduce environmental pollution as well as reduce the cost of importation of wheat.


INTRODUCTION
Citrus is the most abundant crop in the world [1]; with oranges, grapefruits, lemons being the 19 most common citrus fruits. Sweet orange (Citrus sinensis) is the most widely grown of the 20 citrus trees. As of 2010, Brazil was the world's largest producer of oranges, with an output of 21 18.1 million tons. This was followed by America and India which produced 7.5 and 6.0 million 22 tons respectively [2].Oranges are mainly processed to obtain juice. They are also used to 23 produce jams and marmalade. For some time the food industry has shown a special interest 24 in finding uses for citrus industry by-products [3]. Sweet orange oil is a by-product of the 25 juice industry produced by pressing the peel. It is used for flavouring food and drinks and 26 also in the perfume industry and aromatherapy for its fragrance. The edible portion of the 27 orange is referred to as the endocarp and surrounding the endocarp, is the peel. The peel 28 consists of the flavedo and albedo which could be considered as potential sources of fibre 29 and phytochemicals [4]. The roles of fibre and phytochemicals in sustaining good health 30 cannot be over-emphasized. The benefits of fibre in diets include promotion of digestive 31 health and weight loss, control of blood sugar levels and prevention of Type 2 diabetes. 32 Other benefits include lowering cholesterol, indirectly preventing heart disease and stroke 33 [5]. Phytochemicals are non-nutritive plant chemicals that have either protective or disease 34 protective properties. Dietary intake of phytochemicals may promote health benefits, 35 protecting against chronic degenerative disorders, such as cancer, cardiovascular and 36 neurodegenerative diseases [6]. 37 Bread and bakery products are widely consumed throughout the world and bread has been 38 an important food and energy source throughout human history. Wheat flour used in bread 39 production is generally low in fibre and phytochemicals. Since orange peel has been 40 reported to be a source of fibre and phytochemicals, its flour could help in boosting the fibre 41 and phytochemical levels of bread.

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Fully ripened sweet oranges (Citrus sinensis), wheat flour and other ingredients used for 53 bread production were purchased from a retail outlet in Abakaliki, Ebonyi State, Nigeria. 54 55

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Oranges were thoroughly washed with tap water and peeled. The peels were boiled in water 57 (1:4; peels: water) for 10mins and sundried for two days at an average temperature of 34-58 36 0 C. Afterwards, the dried peels were ground into flour and sieved to a particle size of less 59 than 0.2mm. The flour was stored at room temperature in plastic airtight containers until 60 needed. 61 62

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Bread was produced by replacing wheat flour with 3, 6 and 9% orange peel flour (OPF). A 64 sample without the addition of orange peel flour (0% OPF) was used as the control. The 65 bread was produced using the straight dough method described by Mepba

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Tannins were measured using the Folin-Denis spectrophotometric method as described by 79 Pearson [10]. The gravimetric method as described by Harbone [11] was used to determine 80 the alkaloid contents of the bread samples while the quantitative method described by 81 Pearson [10] was used to determine the saponin contents of the bread samples. 82 2.6 Baking characteristics of Bread. 83 Loaf volume was measured using the method described by Hallen et al. [12] with slight 84 modifications. The loaf was put in a metallic container with known volume (V C ). The 85 container was topped up with rice grains, the loaf removed and the volume of the rice noted 86 (V R ). Loaf volume (V L ) could then be calculated and recorded according to After cooling for 1h, the same loaves used for measuring volume were weighed on an 89 electronic balance. Specific volume (V S ) of bread was calculated as: 90 The pH was determined by directly from the samples using a pH meter. Oven spring was 93 determined by measuring the difference in the height of the sample before and after baking 94 [8]. 95 2.7 Sensory evaluation. 96 Sensory evaluation was carried out twenty four hours after preparation of the bread samples. 97 The

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The proximate composition of bread samples produced is shown in values obtained in this work. Increase in the level of OPF in the bread led to a significant 120 (P=.05) reduction in the protein and fat contents of the bread samples. This could be due to 121 the low protein and fat contents of the orange peel. Conversely, increase in OPF resulted in 122 increased levels of fibre and ash which were significant at (P=.05). Ash content is an 123 indication of the level of minerals present in a food material. Increased levels of minerals 124 with increase in OPF levels could be due to high levels of minerals in orange peels. This 125 suggests that orange peels can help in boosting the mineral content of wheat bread. Fibre 126 has been reported to have many health benefits; it has been reported to prevent certain 127 cancers and even lower the risk of developing hemorrhoids [14]. The increase in fibre 128 content with increase in OPF level should therefore, attract acceptability by many consumers 129 as most of our diets are low in fibre but high in fats and carbohydrates. It was also observed 130 that as the fibre content of bread samples increased, there was a reduction in the moisture 131 content. Fibre has been reported to have a high water binding capacity [15]. Therefore, 132 increase in fibre content may have resulted to decrease in moisture content of the bread 133 samples. Calorie content of the bread samples ranged between 267.0 and 287.85kcal/100g. 134 Bread produced with 0% OPF had the highest caloric value while that produced with 9% 135 OPF had the least caloric value. Salgado et al. [13] observed that bread produced with 136 higher levels of cupuassu peel flour exhibited lower calorie factors when compared to those 137 produced with lower levels of peel flour. They suggested that the low calorie factors 138 observed in bread with high levels of peel flour may be associated with the replacement of 139 carbohydrates from wheat flour by the complex polysaccharide fibre in the fruits peel.

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The levels of some phytochemicals in bread produced are presented in Table 2. The 149 presence of phytochemicals in food could provide beneficial health effects to the consumer 150 [6]. For all the phytochemicals studied, 0% OPF had the lowest value while 9% OPF had the 151 highest value. Increased levels of OPF led to increase in the levels of phytochemicals. This 152 result confirms reports that orange peels contain phytochemicals [4]. With respect to the 153 tannins, there was no significant difference between samples containing OPF whilst for 154 alkaloids, bread sample with 3%OPF did not significantly differ from the control. Tannins and 155 saponins have been reported to have antioxidant and anti-mutagenic properties while 156 alkaloids have anti-inflammatory and antioxidant properties [16]. These substances when 157 present in high concentrations, could have toxic effects on the consumers but all the levels 158 present in this study were within safe limits [17].

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The baking characteristics of the bread samples are presented in Table 3. The weight, 167 volume, specific volume and oven spring of the bread samples decreased with increase in 168 OPF. The reason for this trend could be due to the reduction in the amount of gluten and a 169 lower ability of the dough to enclose air [18]. Gluten is responsible for the elasticity of the 170 dough by causing it to extend and trap carbon (IV) oxide generated by yeast during 171 fermentation. When gluten coagulates under the influence of heat during baking, it serves as 172 a framework for the loaf, which becomes relatively rigid and does not collapse [8]. Increased 173 substitution with OPF may have reduced the gluten content and this might explain the 174 observed decreases in some of the baking characteristics. As seen in Table 1

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This study investigated the potentials of OPF in bread production. The use of OPF in bread 210 has the advantage of improving the fibre, ash and phytochemicals levels in bread. However 211 only bread produced with 3% OPF had acceptable sensory quality. This bread had sensory 212 quality comparable to bread made with 0% OPF and is therefore recommended for practical 213 purposes. Other samples showed depressed loaf volume and oven spring. The use of OPF 214 in bread production will not only add value to food but also reduce environmental pollution as 215 well as reduce the cost of importation of wheat. 216 217 218 219 220 221