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

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

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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.






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