PROJECT

A STUDY TO DETERMINE ACIDIC CONTEXT PERCENTAGE OF ASCORBIC IN

FRESH FRUITS JUICES

PRESENTED TO THE KENYA NATIONAL EXAMINATION COUNCIL IN PARTIAL

FULFILLMENT FOR THE AWARD OF CERTIFICATE IN SCIENCE LABORATORY
TECHNOLOGY

PRESENTED BY:
DENNIS MUTUGI
INDEX: 3041010294
TELEPHONE: 0746645000
EMAIL ADDRESS: dmutugi914@gmail.com
DECLARATION
I Dennis Mutugi declare that this is my original work and it has not been presented in any college
or university for award or whatsoever.

STUDENT NAME: …………………………………

DATE:………………………………………………

SUPERVISOR NAME

NAME: ……………………………………………………………

SIGNATURE: ……………………………………………………..

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ACKNOWLEDGEMENT
I take this opportunity to acknowledge the entire Meru National Polytechnic fraternity for the
support they have offered to me and more so my supervisor, who has been training me on how to
write a business proposal I am so much humbled for guiding me to come up with the best of my
degradation on business proposal. God bless you.

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DEDICATION
This project is dedicated to my mom Winfred, for her support financial and the guidance they
have given when writing this research. Also To my lecturers for their time and effort to skills
and knowledge with respect to this project.

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Table of Contents
DECLARATION..............................................................................................................................................2
ACKNOWLEDGEMENT.................................................................................................................................3
DEDICATION................................................................................................................................................4
ABSTRACT....................................................................................................................................................6
CHAPTER ONE..............................................................................................................................................7
1.1 Introduction.......................................................................................................................................7
CHAPTER TWO.............................................................................................................................................8
2.0 Materials and Methods.....................................................................................................................8
2.1 Sample Collection.........................................................................................................................8
2.2 Juice preparation...........................................................................................................................8
2.3 Proximate Analysis.........................................................................................................................8
2.4 Mineral Analysis.............................................................................................................................8
CHAPTER THREE........................................................................................................................................10
3.0 Results and Discussion.....................................................................................................................10
CHAPTER FOUR..........................................................................................................................................16
4.0 Conclusion and Recommendations..................................................................................................16
5.0 References...........................................................................................................................................17

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ABSTRACT
A method was developed of assessing ascorbic acid concentration in fruit juices and wines by
differential pulse, voltammetry. The oxidation peak of ascorbic acid occurs at about 530 mv
( vesus scf) on a pt strip working electrode working at about 470mv on a carbon paste working
electrode. The influence of the operational parameters like the pulse amplitude and the pulse
period on the analytical signal was investigated. The obtained calibration group shows liner
dependence between the peak height and ascorbic acid concentration and within the range 0.31-
20mm with a pt working electrode and within the range 0.07- 20mm with a carbon based
electrode. The equation of the calibration graph was y-21.839x +35.726, y2 =0.9940 when apt
stip electrode was used (where Y represents the value of the current integrity measured for the
peak height, expressed as ua and x the analyze concentration as mm) Rsd=2.09%, N=10,
C(Ascorbic Acid)=2.5mm. The Equation of the calibration graph was y=3.44294+5.7334, r2
=0.9971, when a carbon paste electrodes was used (where y represents the value of intensity
measured for e peak height expressed as ua and x the analyze concentration as mm) r.s.d=
2.55%n= 10, c=( ascorbic acid)= 2.5mm. The developed method was applied to ascorbic acid
assessments in fruit juices and wine. The ascorbic acid determined ranged between 6.83mg/100ml
juice for soft drinks(Fanta madness) and 5.47mg/100ml for citrus(lemon) juices obtained by
squeezing fruit different ascorbic acid concentration(from standard solutions)were added to the
analyzed samples, the degree of recovery being comprised between 94.74 and 104.97%. The
results of ascorbic being assessment by differential pulse voltammetry were compared with those
obtained by cyclic voltammetry. The results obtained by the two methods were in good
agreement.

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CHAPTER ONE

1.1 Introduction
Oranges, Citrus sinensis has three genera and about eighteen defined species (Etebu et al., 2014).
It is cultivated on a very large scale in Nigeria and other tropical and subtropical countries of the
world (Etebu et al., 2014). Global production figures, according to FAO Statistics (2006), stands
at about 108 million tons. Citrus sinensis are considered one of the most important fruit crops in
the tropical and sub tropical regions of the world. They contribute to the diets of several persons
globally and are highly cherished due to their nutritional value (Ubani and Okonkwo, 2011).
Natural foods especially citrus fruits play a major role in human nutrition as they are excellent
sources of antioxidants such as ascorbic acid, carotenoids; tocophenol and phenolic compounds
(Lawal 2007; Morand et al., 2012). It also contains a variety of other nutrients such as proteins,
carbohydrate and some minerals. Ascorbic acid (vitamin C) is the most abundant nutrient in
orange fruits, it is essential for the synthesis of collagen and a lack of vitamin C leads to scurvy
which causes loss of teeth. Vitamin C has a wide range of other beneficial effects on good health (
Zvaigzne et al., 2009)
By definition, according to the united state code of federal regulations, Orange juice is referred to
an unfermented juice obtained from mature oranges of the species Citrus sinensis. It has been
scientifically established that orange juice by virtue of its richness in vitamin and other
antioxidant such as hesperidins, flavonone etc and minerals have many proven health benefits
( Morand et al., 2012)
In order to ensure proper long term preservation, storage, decreased transportation cost, inhibit
microbial growth and off season availability of juice, orange fruits are been subjected to
processing usually on industrial scale. The processing technique adopted by industries such as
freezing, pasteurization and concentration have been proven to have effect on the nutritional
composition of the juice product obtained as most of the natural nutrient are either lost or
degraded during processing (Goyle and Ojha, 1998), the taste, aroma and colour of the juice are
also lost (Zvaigzne et al., 2009). Although effective majors to replenish these lost nutrient by
fortification of juice with extras vitamins or supplement nutrients such as vitamin C and less
commonly vitamins A, E and Beta- carotene are been employed. There are concerns about the
stability of these added vitamins and nutrients (Nelson and Tressler 1980).
On the other hand freshly squeezed orange juice is next to consuming orange itself and there is no
need for fortification because no loss in nutrient occurs unlike the processed.
The persistent problem of post harvest losses of the fruits at farm, home, and in the market has
remain a problem to all stakeholders (Ubani and Okonkwo, 2011). Thus, the need to process the
fruits into less perishable forms cannot be over emphasized. Therefore, the aim of this study was
to compare the nutrient content of freshly squeezed orange juice and that of processed orange
juices.

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CHAPTER TWO

2.0 Materials and Methods

2.1 Sample Collection
Four samples were used for analysis in this experiment, two brands of processed orange juice: fumman
orange juice and chi-exotic orange juice were obtained from north bank market, Makurdi metropolis.
Two varieties of fresh orange, valencia and Ibadan sweet orange used in making freshly squeezed juice
were obtained fresh from orange tree within makurdi metropolis. Valencia orange has a thick and rough
peel and a high amount of seeds while the Ibadan sweet orange has a thin and smooth peel with few
amount seeds.

2.2 Juice preparation

Fresh oranges were carefully peeled and juice was obtained using a juicer (model no; NJ-465, Naka Japan)
and then filtered to remove pulps and seeds. According to the manufacturer’s label , fumman orange
juice was made from orange concentrate while chi-exotic juice was made from orange concentrate and
orange pulp.

The analysis was carried out in duplicates and the following parameters were considered: moisture
content, protein, ash content, fibre, vitamin C, and some minerals including potassium, calcium, sodium
and iron.

2.3 Proximate Analysis

Moisture content, ash content, crude fibre, crude protein and fat content were all determined using the
methods as described by AOAC (2010).

Carbohydrates

Total carbohydrate was calculated by difference using the formula;

%C = 100 - (%P + %F + %A + %W + %Fi)
Where; %C = percentage carbohydrates
%P = percentage of protein
%F = percentage of fat
%A = percentage of Ash
%W = percentage water
%Fi = Percentage of
fibre Vitamin C was determined using methods as described
by AOAC (2010).

2.4 Mineral Analysis

One gram of the respective ash sample was weighed using an electronic analytical balance into a
digestion tube and 20 ml of acid mixture (650 ml conc. Nitric acid, HNO3 ) 80 ml perchloric acid ( PCA )
and 20 ml conc. Sulphuric acid (H2SO4) was added. The flasks were then heated under khjeldal digestion
unit until a clear digest was obtained.

The digest was diluted with distilled water to 100 ml. Standard solution were prepared for each of the

parameter; calcium, sodium, iron and potassium following standard protocols.

Wavelengths of maximum absorbance were determined for each standard using UNICO UV 2100
spectrophotometer. Absorbances of the various standards were obtained and the maximum absorbance

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was selected with its corresponding wavelength. The selected wavelengths were used to measure the
absorbance of the concentration of the samples.
Calculations: Conc. of sample = Ab. of sample × conc. of std.
Ab. of std
Ab sample = absorbance of sample
Ab std = absorbance of standard
Conc. of Std. = concentration of standard (IITA, 2000).

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CHAPTER THREE

3.0 Results and Discussion

Figures 1 – 6 show the proximate composition of the different samples investigated.

Samples contained quite a high amount of carbohydrates. Valencia had the highest carbohydrate content
(13.555%), while Ibadan sweet, fumman and chi-exotic had 13.085%, 11.425% and 10.619% respectively.
These values are higher than the 9.35% reported by USDA nutrient database (2014). For the freshly
prepared orange juices samples, this could be due to the differences in varieties. These are thought to
have developed distinct sugar synthetic biochemical capabilities. The synthetic ones employ the use of
concentrates, whose mixture proportion is determined by the respective company’s formula. This is
thought to constitute a major cause of the differences. Considering the physiological role of
carbohydrates in the body, and sucrose, the main sugar in oranges fruits, it is good to note the significant
contribution oranges make to the caloric content of a diet, especially when consumed in the fresh state.

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 16

14

12

10
Carbonhydrate Content (%)

Ibadan Sweet Valencia Fumman Chi- exoctic

Orange
Fig. 1: % Carbonhydrate Content in four orange juices

The crude protein of both freshly squeezed orange juice and processed varied, especially between the
fresh juices and the processed ones. Valencia orange juice had the highest amount of crude protein (385
mg/100g) while Ibadan sweet orange had a value of 350 mg/100g. fumman and chi-exotic orange juice had
crude protein of 328 mg/100g and 241 mg/100g respectively (fig. 2). These values are far less than the 940 mg
reported by USDA Nutrient Database (2014). Nzeagwu and Onimawo (2010) reported 1.007%/100ml of crude
protein from freshly prepared juice of Eugenia unifloraL (Pitanga cherry) juice. This shows that orange juice is
rich in crude protein. These results observed for the freshly squeezed juices were quite higher than those
obtained Peter et al, (2009). The crude protein value for fumman corresponded with that reported on the
package.
450
400

350

300

250

200

150 Protein Content (mg/100g)

100
50

0
Ibadan Sweet Valencia Fumman Chi- exoctic
Orange
Fig.2: Protein Content (mg/100g) of four orange juices

10
 50
45

40

35

30

25

20
Ash Content (mg/100g)
15

10

5 Ibadan Sweet Valencia Fumman Chi- exoctic

Orange

Fig. 3: Ash Content (mg/100 g) in four orange juices

The ash content ranged from 32 mg/100g in the processed chi-exotic brand to 45 mg/100g in the freshly
squeezed Ibadan sweet orange juice, with a mean value of 38 mg/100g. Although the freshly squeezed juice had
higher value of ash than the processed ones, there was no significant difference (p<0.05) between them. The ash
content of freshly squeezed juices were lower than those reported by Onibon et al. (2007) but were in agreement
with those reported by Peter et al. (2004).
The result of the fibre content (fig. 4) shows that both varieties of freshly squeezed juice contained the
same amount of fibre (20 mg/100g). Fumman and chi-exotic orange juice contained 12 mg/100g and 8 mg/100g
respectively. USDA Nutrient Database (2014) reported no dietary fibre component of 2.4 g/100g. This large
difference could be attributed to differences in varieties, among other factors. Nzeagwu and Onimawo (2010)
reported 0.553%/100ml of fibre in Eugenia uniforaL.
The experimental procedure showed a result wherein fats were not detected. This however, contradicts
the report of USDA Nutrient Database (2014) which reported as much as 120 mg/100ml of fat. This also agrees
with the nutritional information label placed on Fumman package.
25

20

15

10

Fibre Content (mg/100g)

5

0
Ibadan Sweet Valencia Fumman Chi- exoctic
Orange

Fig.4: Fibre Content (mg/100 g) in four samples of orange juices

Ibadan sweet orange had the highest vitamin C (ascorbic acid) content of 10 mg/100g while Valencia

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orange juice had of 8.0 mg/100g, fumman orange juice contained 2.30mg/100g and chi-exotic
orange juice contained 2.56 mg/100g (fig.5). This agrees with the result obtained by Zvaigzne
et al. (2009). However, it is far lower than the 53.2 mg/100g reported by USDA Nutrient
Database (2014). From this result, freshly squeezed juice contains more vitamin C than
processed juice. Ascorbic acid is highly oxidizable in the presence of atmospheric oxygen.
Thus, this could have affected the total content of the vitamin in the juices. Moreover, in the
processed samples, this relatively low vitamin content could be due to the high rate of dilution
during reconstitution or loss as a result of heat.
This shows that freshly squeezed orange juice can contribute substantially to the 45
mg WHO/FAO (2004) daily recommended dietary allowance of vitamin C. From the result of
this study, processed oranges are useful as food supplements to prevent vitamin C deficiency.

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10

Vitamin (mg/100 g)
2

Ibadan Sweet Valencia Fumman Chi- exoctic

Orange

Fig. 5: Vitamin C content (mg/100g) in four samples of orange juices

The moisture content varied from 86.00% in valencia orange variety to 89.10% in chi-exotic
orange juice with a mean value of 87.45% (fig. 6). Among the processed orange juices, chi-exotic had
the highest moisture content of 89.10% while fumman had a moisture content of 88.20%. Among the
freshly squeezed orange juice, Ibadan sweet orange variety had a moisture content of 86.00%. The
moisture content of freshly squeezed orange varieties were quite lower than those reported by Onibon
et al. (2012) (Within the 1st to 7th day of storage). However, they were in agreement with the 86.75%
reported by USDA Nutrient Database (2014). Moisture content of fumman orange juice is within the
range of values disclosed on the package.
Considering the high moisture content, it is believed that oranges or orange juices can be a
good source of water in the body especially during seasons of decreased appetites when water intake is
no longer appealing.

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89.5
89

88.5

88

87.5

87

86.5
Moisture Content (%)
86

85.5

85 Ibadan Sweet Valencia Fumman Chi- exoctic

Orange

Fig. 6: Moisture Content (%) in four orange juices

0.35

0.3

0.25
Ibadan sweet
Valencia
0.2

Fumman
Chi-exotic
0
Calcium Potassium Sodium Iron

Fig. 7: Mineral composition (ppm) of different oranges juices

The result of the mineral concentration of the samples is shown in fig.7 above. It
reveals that fumman oranges juice has the highest amount of calcium (0.050 ppm) followed
by Valencia (0.048 ppm), Ibadan sweet orange juice (0.046 ppm) and chi-exotic oranges
(0.045 ppm). Chi-exotic had the highest amount of sodium (0.3176 ppm), Valencia (0.053
ppm), fumman (0.0523 ppm) and Ibadan sweet (0.0515 ppm). Potassium was found to be
higher in Valencia (0.210 ppm) than in chi- exotic (0.184 ppm), Ibadan sweet orange (0.181
ppm) and Fumman (0.131 ppm). USDA Nutrient Database (2014) reported the values for
calcium, iron and potassium to be 40 mg, 0.1 mg and 181 mg respectively.

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 Iron was found to be highest in Chi-exotic (0.1287 ppm), while Fumman, Valencia
and Ibadan sweet had 0.0257 ppm, 0.0142 ppm and 0.0115 ppm respectively in descending
order of magnitude. Prolong consumption of some of these minerals such as iron and sodium
could lead to toxicity in man.
The adequate intakes (AI) of these minerals are 1500 mg/day, 1000 mg/day and 4700
mg/day in both men and women for sodium, calcium and potassium respectively. Iron has a
RDA value of 8 mg/day and 18 mg/day for average men and women respectively. Thus, in
reference to the AI and RDA, orange is not a good source of these minerals and so
cannot be relied upon to provide them. However, these can be easily sourced from other
diets in enough quantities.

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CHAPTER FOUR

4.0 Conclusion and Recommendations

This study hereby corrects the erroneous impression that orange juice is taken to aid digestion and
should be preferentially taken after a meal. The report shows rich sources of nutrients found, especially
in freshly squeezed orange juices actually qualifies it to be taken as a source of food.

Furthermore, the study showed that there was no significant difference between the nutritional
compositions of freshly squeezed orange juice and the processed orange juices except in vitamin C
content. Freshly squeezed orange juice contains more vitamin C the processed ones.

It’s recommended that freshly squeezed juice should be included in the daily diet of both adults and
children, due to its nutritional benefits so outlined above. Manufacturers of processed juices should be
encouraged to state the nutritional content of their products on the package so that individuals can be
aware of the amount of nutrients obtainable from the products they buy.

Further studies should be carried out on the effects of additives in processed orange juice and the anti-
nutrients present in these additives since measures have been taken to reduce to loss of nutrients
during processing.

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5.0 References
Association of Official Analytical Chemists, (AOAC) (1990). Official methods of analysis, Association of
Official Analytical Chemists, Washington D.C (15th ed.)
Association of Official Analytical Chemists, (AOAC) (2010). Official method of analysis, Association of
Official Analytical Chemists, Washington D.C (18th ed.)
Etebu, E. and Nwauzoma, A.B. (2014). A review on sweet orange (Citrus sinensis L osbeck): Health, Diseases
and Management. Afr. J. Res. Comm. 2(2):33-70.
Food and Agriculture Organization of the United Nations (2006). (FAO Statistics)
Goyle, A. and Ojha, P. (1998). Effect of storage on vitamin C, microbial load and sensory attributes of orange
juice. J. Food Sc. Tech. (35): 346-348.
International Institute of Tropical Agriculture, IITA, (2000). Methods of mineral analysis.www.iita.org.
Lawal, M.A. (2007). Efficiency of sweet orange production among small scale farmers in osun state , Nigeria.
Afr. J. Gen. Agric. 3(2). 127-132.
Morand, C., Claude, D., Dragan, M., Delphine, L., Jean F.M. and Augustin, S (2011): Herperidins contributes
to the vascular protective effect of orange juice, a randomized crossover study in healthy
volunteers. Am. J. Cli. Nut. (93): 73-80.
Nelson, P. E. and Tressler, D. K. (1980). Fruit and juice vegetable processing technology 3 rd ed. Avi publishing
Co.
Nzeagwu, O.C., and Onimawo, I.A. (2010). Nutrient composition and sensory properties of juice made from
pitanga cherry (Euglena uniflora L.) fruits. Afr. J. Food Agric. Nut. Dev. 10(4):2379-2393

Onibon, V.O., Abulade, F.O. and Lawal, L. O. (2007). Nutritional and anti-nutritional composition of some
Nigerian fruits. J. Food Tech. 5(2):120-122.
Pasha, A.R., Butt, M.S., and Mohyuddin, M.M. (1994). Quality evaluation of some commercially manufactured
fruit beverages. Pak. J. Agric. Sc. 3(3): 19-24
Peter, A.I., John, J.M., and Mohammed, A. (2010). Effect of storage period on some nutritional properties of
oranges and tomato Au. J. Tech. 13(3):181-185.
Pilar, R., Perez, C., and Russell, R. (2008). Processing and storage effects on orange juice aroma. J. Agric. Food
Chem. 56(21): 9785-9796.
Ubani, O.N., and Okonkwo, E.U. (2011). A review of shelf life extension studies of Nigerian indigenous fresh
fruits and vegetables in the Nigerian stored products research institute. Afri. J. Plant Sci. 5(10):537
- 546
USDA Nutrient Database (2014). United States Department of Agriculture, National Nutrient Database for
Standard Reference Release 26, Fruits and Fruit Juices
WHO/FAO (2004). World Health Organisation and Food and Agricultural Organization of the United Nations.
Vitamins and mineral requirements in human nutrition. Pp 130-139.
Zakpaa, H.D., Mak-Mensah, E.E., and Adubofour, J. (2010). Production and characterization of flour produced
from ripe “apam” plantain (Musa sapientum L. var. paradisiacal; French horn) grown in Ghana. J.
Agric. Biotech. Sust. Dev. 2(6):92-99
Zvaigzne, G. Karklina, D. Seglina and Krasnova, I (2009): Antioxidants in various citrus juices. Chem. Techn..
3(52):56-62.

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