ABSTRACT
Sweet orange (Citrus sinensis) fruits were washed, peeled manually, the juice extracted and the seeds were removed. The peels and pulps were sliced into thin slices of about 2 cm thick, sun dried at 30 ± 2°C to constant weight, milled and sieved to obtain orange peel and orange pulp flours, respectively. The orange peel and pulp flours, respectively were used to substitute wheat flour 5, 10 and 15 % respectively. The flours were analyzed for their chemical composition. Biscuits were prepared from the flour blends and evaluated for their chemical composition, sensory and storage properties. Antioxidant activities of water and ethanol extracts of flours and biscuits were determined. Bioassay study in which five weeks old Wistar rats weighing between 80 and 90 grams were divided into four groups containing six rats each was carried out. Groups 1,2,3 and 4 were fed biscuits containing 10 % orange peel flour, 10 % orange pulp flour, 100 % wheat flour, and normal feed (growers mash), respectively. Feed intake, water intake, changes in body weight, blood sugar and lipid profile of the rats were determined. Biscuit samples were stored for six months at 30 ± 2°C and 80 to 90 % relative humidity. Changes in pH, moisture and peroxide value of the biscuits were assessed monthly. The sensory properties of the stored biscuits were also evaluated after every two months of storage. The results showed that the orange pulp flour was significantly higher (p<0.05) in fibre, ash and moisture but lower in fat and carbohydrate contents than the orange peel flour. The mineral contents of the flours were not significantly different (p>0.05).The orange peel flour contained more tannins than the pulp flour, but the flours were not significantly different in their oxalates contents. However, orange peel flour was significantly higher (p<0.05) than the pulp flour in alkaloids, flavonoids, anthocyanins and carotenoids. The biscuit samples containing 10 % orange pulp had higher fibre content than the biscuit containing 10 % peel flour. The mineral contents did not differ significantly (p>0.05) among the biscuits. Baking reduced all the antinutrients of the biscuit samples. The highest antioxidant activity was shown by the ethanol extracts of the flours and biscuit samples in relation to the water extracts. Body weights of all the rats in all the groups increased during the study period. The rats fed biscuits containing 10 % peel and pulp flours showed least increase in body weight. There were increases in the high density lipoprotein and total cholesterol contents in all the rat groups. However, the low density lipoprotein (bad cholesterol) of the rat groups decreased. The triglyceride contents increased in all the rat groups except for the group fed biscuit containing 100 % wheat flour. The rats fed 10 % orange peel and pulp flour biscuits also showed lower blood glucose levels than the other groups. There were no significant differences (p>0.05) between the peel and pulp biscuits in colour and texture at the end of six months storage. However, the biscuits containing orange peel had higher ratings for flavour, but lower ratings for taste and overall acceptability. Moisture contents of biscuits fluctuated during storage, values ranged between 5.56 and 8.85 %. The peroxide values of the biscuits increased slightly after 4 months of storage.
CHAPTER ONE
1.0 INTRODUCTION
Sweet orange is one of the most important fruits in the tropical and sub-tropical regions of the world. The fruits are usually eaten fresh but are also used for making canned orange juice, frozen juice concentrate, jams, jellies among others. Orange processing industries generate huge amounts of orange peel and pulp as by products from the industrial extraction of orange juices. These peel and pulp contain among other things high levels of vitamin C, dietary fibre and flavonoids. Dietary fibre has been used for the treatment of various gastrointestinal disorders and for such possible health benefits as lowering cholesterol levels, reducing risk of colon cancer and losing weight (Friedman, 1989). Dietary fibre has also been reported to have some nutraceutical potentials (Weingartner et al., 2008). Orange peel and pulp also contain other phytochemicals such as polymethoxylated flavones (PMF) and hesperidin which have hormonal and antioxidant actions and are also involved in enzyme stimulation (Gardon, 1990).
Until just recently, analysis of food was limited to sensory and its nutritional value. However, there is growing evidence that other components of food may play an integral role in the link between food and health (Kaira, 2003). Consumers are increasingly interested in the health benefits of food and have begun to look beyond the basic nutritional benefits to the potential disease prevention and health enhancing compounds contained in many foods (Hasler, 2003).
Nutraceutical, a term combining the words “nutrition and pharmaceutical,” is a food with a medical health benefit, including prevention and treatment of disease. This definition includes any substance that may be considered a food or part of a food and provides medical or health benefits, including the prevention and treatment of disease. Such products may range from isolated nutrients, dietary supplements and diets to genetically engineered foods, herbal products and processed foods such as cereals, soups, beverages among others. (Defelice, 1994). Examples of foods with nutraceutical values are broccoli (Sulforphane), which may help in the prevention of cancer, resveratrol from red grape products as an antioxidant, flavonoids in citrus, tea, wine and dark chocolate (Weingartner et al., 2008). Many botanical and herbal extracts such as ginseng, garlic oil etc have been developed as nutraceuticals. The use of nutraceuticals to accomplish desirable therapeutic outcomes with reduced side effects as compared with other therapeutic agents has met with great success (Whitman, 2001; Nelson, 1999). The peel and pulp of orange fruits have been noted to contain some bioactive substances believed to possess nutraceutical potentials (Kootstra, 1994). Thus, the incorporation of orange peel and pulp into wheat flour for the production of biscuit would enhance greater utilization of phytochemicals in Nigerian diets.
Biscuit is a confectionary, dried to very low moisture content (Okaka, 1997). Biscuit is a snack food which can be eaten in-between meals or at any time of the day and by any age bracket. An increasing proportion of the household food budget in Nigeria is spent on snacks in which convenience and quality are perceived as most important (Lasekan and Akintola, 2002). Biscuits contain fat (18.5 %), carbohydrate (78.23%), ash (1.0 %) and salt (0.85 %) (Okeagu, 2001). They are generally characterized by a low moisture content (Okaka, 1997), The shelf life is several months under correct storage conditions (Ihekoronye, 1999). However, biscuits must be packaged in containers which prevent moisture uptake (Okaka, 1997).
1.1 STATEMENT OF PROBLEM
The juice obtained from orange fruits is widely consumed while the pulp and peel are discarded. The amount of peel and pulp obtained from citrus fruit processing accounts for 50% of the original amount of the whole fruit (Chon and Chon, 1997). These Peel and Pulp contain some bioactive substances believed to have nutraceutical potentials.
Biscuit consumption among children and adult is high in Nigeria. Orange peel and pulp could be incorporated into wheat for biscuit production because of their phytochemical content. However, the storage properties and nutraceutical potential of biscuit containing orange peel and pulp need to be assessed.
1.2 BROAD OBJECTIVE OF THE STUDY
The broad objective of the study was to determine the chemical composition, health promoting potentials and storage stability of biscuits supplemented with orange peel and pulp flours.
1.3 SPECIFIC OBJECTIVES
1) To produce biscuits from blends of wheat and orange peel and pulp flours.
2) To determine the chemical composition of the biscuits.
3) To evaluate the health promoting potentials of the biscuits using bio-assay study.
4) To determine the storage stability of the biscuits.
CHAPTER TWO
2.0 LITERATURE REVIEW
- The Orange Fruit
Orange belongs to the kingdom plantae and division magnoliophyta. It is of the class magnoliopsida and order sapindalas. Its family is Rutaceae, Genus citrus and specie C. sinensis. It has the binomial name Citrus sinensis (L) Osbeck.
Orange trees have dark green, shiny leaves and small white flowers with five petals. The flowers smell sweet thereby attracting bees. It is an ever green flowering tree generally growing 9 to 10 m in height. The leaves are arranged alternately, they are ovate in shape with crenulate margins and are 4 to 10 cm long. Orange fruit is considered a hesperidium, a kind of modified berry, because it has numerous seeds, fleshy and soft, derives from a single ovary, and is covered by a rind created by a leathery thickening of the ovary wall (Bailey and Bailey, 1976). Inside, the fruit is divided into segments, which have thin tough skins that hold together many little sections with juice inside. Inside the segments of most oranges are the seeds. An orange seed is called a pip. The white thread-like material attached to the inside of the peel is called pith (Bailey and Bailey, 1976). Orange skin is often called “orange peel”. Orange fruit season begins from October and lasts until February.
- Orange Production
Oranges grown for commercial production are grown in groves and are produced throughout the world. Brazil is by far the greatest producing area, followed by Florida, which accounts for 80 % of the United States crop. Benue state in North Central Nigeria accounts for the large production of oranges among other varieties of agricultural produce which are taken daily in truckloads to other markets and other commercial centres across the country (Anon, 2011a).
- Problems of Orange Production and Distribution in Nigeria
Generally, in Nigeria, the great potentials derivable from sweet orange has not been harnessed. Virtually all the oranges produced locally are eaten as fresh fruits. Only a small percentage of produced oranges find their way to the canning industry. The neglect of the orange fruit industry is because investors prefer to invest in food crops such as maize and cassava that can fetch them short-run quick returns, than in the fruit canning industries. This is because the orange industry is constrained by many marketing problems such as heavy crop losses usually while the fruit is being transferred along its marketing chain. Loss in transit is great for orange fruits because the fruits are fragile and juicy (Adeyemi and Ogazi, 1998). At the market place, the seller is also faced with the problem of spoilage as the fruit have to be sold within the shortest time possible before they get spoilt. The orange fruit perishability problem is also compounded by the poor storage/shelf life of the fruit (Babatola, 2004).
Another problem is that of pest and disease attack on the crop. They are attacked by pests and diseases which reduce their market quality and quantity (Apata, 2002). All these factors as well as frequent price fluctuations due to the perishability and seasonal nature discourage prospective investors from venturing into the orange industry (Babatola, 2004, Adeyemi and Ogazi, 1998, Olukusi and Isitor, 1991).
- Varieties of Oranges
Citrus sinensis is classified into four groups with distinct characteristics as common oranges, blood oranges, navel oranges and acidless oranges (Kimball, 1999, Sauls, 1998, Webber et al., 1989). Common oranges (also called “white”, “round” or “blond” oranges) make up about two thirds of all oranges grown and includes the Valencia or Murcia orange which is sweet and used for juice extraction. It is a late season fruit and the Hamlin which is an early-season orange grown in Florida and Brazil for commercial use (Webber et al., 1989).
Navel oranges are characterized by the growth of a second fruit at the apex, which protrudes slightly and resembles a human navel. They are primarily eaten as the skin is thicker and easier to peel than a common orange. They are less juicy, available from November through April, with peak supplies between January and March (Kimball,1999).
Blood oranges are widely grown in Spain and Italy. They are characterized by dark red pigmentation. They are considered, in general the most delicious orange (Kimball, 1999). Other varieties of blood oranges are Tarocco, Moro, Maltese etc.
Acid less oranges are early season fruit with very low levels of acid. They are also called sweet oranges in the US, with similar names in other countries (Kimball, 1999). The lack of acid, which protects orange juice against spoilage in other groups, renders them generally unfit for processing, due to spoilage.
- Chemical Composition of Orange Fruit
Fruit composition is influenced by a large number of natural factors including variety of fruit, geographical location, climatic zone, soil, degree of maturity etc. The composition of juice products may be influenced by technology used in processing and packaging (Sass-Kiss et al., 2003). The edible portion is the endocarp. Surrounding the endocarp is the peel, which comprises 20 to 50 % of the weight of the fruit and consists of flavedo and albedo. The flavedo, or outer peel is a layer of tissue underlying the epidermis and contains the chromoplast and oil sacs. The albedo, or inner peel, is a layer of spongy white tissue which is connected to the core and supplies the water and nutrients from the tree which are necessary for fruit growth and development (Ihekoronye and Ngoddy, 1985).
The proximate composition of the edible portion is water, 86%, protein, 0.6%, fat, 0.1%, micronutrients per 100g: calcium, 24 mg, iron, 0.3 mg, vitamin A, 120 iu, thiamine, 0.06 mg, riboflavin, 0.02 mg, niacin, 0.1mg and ascorbic acid, 36mg. The pH of the orange is around 3.5, the main enzyme system is a methyl esterase which hydrolyses polygalacturonic acid polymethyl esters. The principal pigments which develop on ripening are carotenoids, mainly xanthophylls 5, 6 and 5, 8 – epoxides. The major volatile components of whole oranges are d-limonene, beta-mycrene, alpha pinene, acctaldehyde, octanal, ethanol and ethyl acetate (Ihekoronye and Ngoddy, 1985).
2.6 General uses of Orange
Orange tree is a very useful tree, since every part of it is useful for one purpose or another. Some of the uses of orange include:
- Production of conserve (marmalade). All parts of the orange fruit is used to make marmalade. The pith and pips are separated and placed in a muslin bag where they are boiled in the juice.
- Essential oils neroli, from the flowers and petitgrain from the leaves, are used in perfumery (Ihekoronye and Ngoddy, 1985).
- The petals of orange blossom can also be made into a delicately citrus scented version of rosewater. Orange flower water is a common part of both French and middle Eastern cuisines, most often as an ingredient in desserts and baked goods.
- In Spain, fallen blossoms are dried and then used to make tea.
- Orange leaves can also be boiled to make herbal tea.
- Juice extracted from sweet orange leaves are used to control ulcers, sores etc.
- Orange peel is used by gardeners as a slug repellent.
- The peels are also used for making soaps and perfumes.
- Orange oil is used for flavouring.
- Cooking oil is extracted from the seeds.
- Orange wood is a flavouring wood in meat grilling, as much as oak, pecan and hickery are used.
- Orange wood sticks are used as cuticle pushers in manicure and pedicure.
2.7 Health Benefits of Orange
The fruit is low in calories, contains no saturated fats or cholesterol, but is rich in dietary fiber, pectin, which is very effective in reduction of excess body weight. Pectin by its action as bulk laxative helps to protect the mucous membrane of the colon by decreasing its exposure time to toxic substances as well as by binding to cancer causing chemicals in the colon. Pectin has also been shown to reduce blood cholesterol levels by decreasing its re-absorption in the colon by binding to bile acids in the colon (Umesh, 2009).
Oranges like other citrus fruits, is an excellent source of vitamin C. Vitamin C is a powerful natural antioxidant. Consumption of foods rich in vitamin C helps the body develop resistance against infections agents and scavenge harmful, pro-inflammatory free radicals from the blood. It also offers protection against rheumatoid arthritis, asthma and osteoarthritis.
Orange contains a variety of phytochemicals. Hesperitin and Narigenin are flavonoids found in orange. Narigenins is found to have a bio active effect on human health as anti inflammatory, anti tumour and blood clot inhibiting properties as well as strong antioxidant effects (Boss et al., 1996).
Oranges also contain very good levels of vitamin A, which is required for maintaining healthy mucus membranes and skin and it is essential for vision. It is also a very good source of B-complex vitamins such as thiamin, pyridoxine and folates. These vitamins are essential in that the body requires them from external sources to replenish. Orange fruit also contains a very good amount of nutrients like potassium and calcium. Potassium is an important component of cell and body fluid that help control heart beat rate and blood pressure through countering sodium action (Umesh, 2009) Fibre in the fruit helps to prevent atherosclerosis (hardening of the arteries). A class of components found in the citrus peels, called polymethoxylated flavones (PMFs), have the capability to reduce cholesterol levels (Genera, 2011).
- What is missing in orange juice?
Whole fruit provides more nutrition than fruit juice (Kootstra, 1994). Unfortunately when fruits are juiced, the fruit skin is removed. The edible skins of many of world’s healthiest fruits are all sites of important biological activity in the life of the fruit. The skin is one of the places where the fruit interacts with sunlight, and forms a variety of coloured pigments that absorb different wavelength of light. These pigments, including carotenoids and flavonoids are well researched as components that protect health. Fruit juice that has been robbed of its fiber and broad range of nutrients is basically just a concentrated source of sugar that lacks the supportive nutrients to help it digest and metabolize (Kootstra, 1994).
- Orange Peel
Peel is the thick skin of some fruits and vegetables. Orange peel contains soluble sugars 16.9%, cellulose 9.21%, hemicellulose, 10.5%, and pectin 42.5% (Beatriz et al., 2008). Flavonone in oranges, the hesperidin molecule, has been singled out in phytonutrient research on oranges. Most of the phytonutrients are found in the peel and inner white pulp of the orange rather than in the juice (Brett, 2011).
Although not as juicy or delicious as the inside of an orange, the peel is edible, and has been consumed particularly in environments where there is scarcity of resources and where maximum nutritional value must be derived and minimal waste generated (Gargulinski,2011). However, grating a tablespoon of orange peel each day and using it to flavor tea, salads, salad dressings, soups etc may be a practical way of achieving some cholesterol lowering benefit. Frequently, the extracted essential oils from the orange peels were used for the treatment of indigestion and other illnesses.
During the middle ages, cooks preferably used dried orange peels as flavouring rather than serve the fruit or the juice (Anon, 2012) Orange peels can be made into candies by boiling it in sugar water until they become almost translucent (Anon, 2012) Dried orange peels can be placed in a cloth bag and placed in closets and cupboards to reduce musky odours (Anon, 2012). Orange peels are used to deodorize a garbage disposal unit. Placing orange peel at the bottom of trash can before putting the bags in is said to reduce odour and help discourage insect infestation (Anon, 2012). Orange peels are also combined with carbon dioxide to make a kind of plastic (Anon, 2012). Limonene, which comprises 95 % of the oils in an orange peel is used in all sorts of applications including the manufacture of plastics (Anon, 2012). It is flammable, thus, dried and used for kindling fire. However, they burn slower and steadier than the usual kindling materials like newspapers. As they burn they emit a nice odour (Anon, 2012).
- Orange Pulp
In addition to the skin, which is an important source of fibre in most fruits, the pulpy part of the fruit is also a source of fibre, and other nutrients. The orange pulp contained total pectin 26.0 to 45.6 %, neutral detergent fibre, 15.8 to 31.0 % and crude fibre, 9.9 to 20.6 % (Porzio and Blake, 1983). The white pulpy part of the orange is the primary source of its flavonoids. When the pulpy white part of the orange is removed in the processing of orange juice the flavonoids in the orange are lost in the process. This loss of flavonoids is one of the many reasons for eating the orange in its whole food form (Birt et al., 1996).
Dietary fibre is the indigestible portion of plant foods. It is metabolically inert, absorbing water as it moves through the digestive system, easing defecation (Weickert and Pfeiffer, 2008) The main action of dietary fibre is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed. Soluble fibre binds to bile acids in the small intestine, making them less likely to enter the body, this in turn lower cholesterol levels in the blood (Anderson et al., 2009).
Soluble fibre also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and once fermented in the colon, produces short-chain fatty acids as by products with wide-ranging physiological activities (Weickert and Pfeiffer, 2008). Dietary fibre is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fibre intake (Jones and Varady, 2008, Eastwood and Kritchevsky, 2005). The short chain fatty acids produced are involved in numerous physiological processes promoting health (Wong et al., 2006). These include:
- Stabilize blood glucose levels by acting on pancreatic insulin release and liver control of glycogen breakdown.
- Suppress cholesterol synthesis by the liver and reduce blood levels of low density lipoprotein cholesterol and triglycerides responsible for arthrosclerosis (Wong et al., 2006).
- Lower colonic pH (raises the acidity levels in the colon) which protects the lining from formation of colonic polyps and increases absorption of dietary minerals (Drozdowski et al., 2002).
Much use has not been made of the orange pulp separately, but it can be used creatively in the kitchen. Recipes using orange pulp include oranges and kiwi cocktail recipe and fruit salad with orange pulp dressing e.t.c.
- Phytochemicals
Phytochemicals are non-nutritive plant chemicals that have protective or disease preventive properties. They are nonessential nutrients, meaning that they are not required by the human body for sustaining life. It is well known that plant produce these chemicals to protect themselves but recent research demonstrate that they can also protect humans against diseases. There are more than a thousand known phytochemicals. Some of the well known phytochemicals are lycopene in tomatoes, isoflavones in soy and flavanoids in fruits (Weingartner et al., 2008).
Plants and plant products are being used as a source of medicine since long. According to the world Health Organization (WHO), more than 80 % of the world’s population, mostly in the developing countries depend on traditional plant based medicine for their primary health care needs. India has about 45,000 plants and among them, many have been claimed to possess medicinal properties (Varma, 2008). Foods containing phytochemicals are already part of our daily diet. In fact, most foods contain phytochemicals except for some refined foods such as sugar or alcohol. Some foods such as whole grains, vegetables, fruits, herbs etc, contain many phytochemicals. The easiest way to get more phytochemicals is to eat more fruits and vegetables ((Weingartner et al., 2008).
There is evidence from laboratory studies that phytochemicals in fruits and vegetables may reduce the risk of cancer possibly due to its content of dietary fibers, polyphenol antioxidants and ant-inflammatory effects.(Brown and Arthur, 2001). An important cancer drug, Taxol, is a phytochemical initially extracted and purified from the pacific yew tree (Brown and Arthur, 2001).
