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
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.
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).
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).
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).
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
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).
CHEMICAL COMPOSITION, HEALTH PROMOTING POTENTIALS AND STORAGE PROPERTIES OF BISCUITS SUPPLEMENTED WITH ORANGE PEEL AND PULP FLOURS
