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International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-4, July-Aug- 2017
http://dx.doi.org/10.22161/ijeab/2.4.80 ISSN: 2456-1878
www.ijeab.com Page | 2201
Analysis of Physical and Chemical Composition
of Sweet Orange (Citrus sinensis) Peels
Oyebola O. Olabinjo1 *, Agboola S. Ogunlowo1, Olabode O. Ajayi2, Ayoola P. Olalusi1
1Department of Agricultural and Environmental Engineering, Federal University of Technology, Akure, Ondo State, Nigeria.
2Department of Chemistry, Federal University of Technology, Akure, Ondo State, Nigeria.
Abstract— Sweet orange is one of the most common fruits
in the World. The waste generated from the fruits needs to
be put into a beneficial use. In this study some physical
and chemical properties of the primary waste of sweet
orange was investigated. The result showed sweet orange
rinds (peels) as the major waste and contains 45-50% of
the total mass of sweet orange fruits. The chemical
analysis showed sweet orange rinds to be rich in protein
of 7.15% and crude fibre of 12.79% which can be used as
ingredients in processed food. These uses will promote
sustainable disposal of orange rinds.
Keywords— Orange rinds, proximate analysis, protein,
crude fibre.
I. INTRODUCTION
Citrus (citrus spp) is one of the most abundant fruit crops
with World production estimated at 115 million tons per
year. Citrus is a large family whose dominant members
include sweet oranges (Citrus sinensis),
tangerines/mandarin (Citrus reticulata), lemon (Citrus
limon), limes (several species) and grape fruits (Citrus
paradis). Citrus fruits are notable for their fragrance,
partly due to flavonoids and limonoids contained in the
rinds (Manthey, 2004). Also, citrus fruits and juices are
important sources of bioactive materials including
antioxidants such as ascorbic acid, flavonoids and
phenolic compounds that are important to human nutrition
(Kamran et al., 2009).Citrus fruits are good source of
folic acid, vitamin B (thiamine), potassium, phosphorus,
calcium, iron, magnesium, sodium and sulphur (Nagy et
al., 2007).
The endocarp is rich in soluble sugar and contains
significant amounts of vitamin C, pectin, fibres, different
organic acids and potassium salt which give the fruits its
characteristic “citrus flavour” (Ezejioforet al., 2011).
Africa produces 3,741,000 tonnes of varieties of citrus
fruits of which Nigeria contributes 3,240,000 tonnes
(FAO, 2004). Nigeria produces 3% of fresh citrus in the
World (FAO, 2004). The rinds (peels) obtained from the
pericarp of these fresh fruits are available in large
quantities during the citrus season thereby constituting
environmental problems since it is not being put into any
productive use. The production of citrus fruits in Nigeria
is significant, with heavy direct consumption due to few
and small capacity processing industries to convert the
fruit to juice, concentrate and canned fruit.
The inability of the few and small capacity processing
industries to convert the fruit juice and concentrate has
led to the generation of wastes. Waste is anything in a
ruined or devastated condition (merriamwebster). It can
also be defined as any unavoidable material resulting
from an activity, which has no immediate economic
demand and which must be disposed of (NISP, 2003).
Physical properties are important in many problems
associated with the design of machines and the analysis of
the behaviour of the product during agricultural
processing such as extraction of phytochemicals. Physical
characteristics of agricultural products are the most
important parameters for determination of proper
standards to design of grading, conveying, processing,
and packaging systems (Tabatabaeefar, and Rajabipour,
2005, Karimiet al., 2009). The food industry has shown a
special interest in finding uses for citrus industry by-
products. Hence the need to know the physical and
nutrient component of the peels.
II. MATERIALS AND METHODS
2.1 Raw material characterization
Harvested sweet orange was obtained from a fruit and
vegetable market centre from a local market in Akure,
Ondo State, Nigeria. The samples were selected manually
from unripe and overripe fruits, thus providing a uniform
samples or fruits of the relatively same ripeness stage.
The ripe fruits were processed at the Crop Processing
Laboratory of Agricultural and Environmental
Engineering, Federal University of Technology Akure.
These fruits were washed to remove dirt’s and foreign
materials from the epicarp. The fruits were peeled with
knife to remove epicarp or rind or flavedo or shell.
2.1.1 Physical Properties of Citrus species
a. Weight determination
The weights of the selected agricultural materials were
determined using a method described by Varnamkhastiet
al. (2007). The materials were randomly selected from
each sample into flat plates which were carefully weighed
using an electronic balance to an accuracy of 0.01g. The
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-4, July-Aug- 2017
http://dx.doi.org/10.22161/ijeab/2.4.80 ISSN: 2456-1878
www.ijeab.com Page | 2202
procedure is replicated three times for each sample, and
average value was taken and recorded.
b. Volume determination
The volume of the fruits and peels were determined by
filling a 250 ml measuring cylinder with 150 ml of water.
The whole fruits and peels of each variety (separately)
were immersed in the water. The amount of displacement
in water was recorded. The procedure is replicated three
times and volume was calculated as:
(1)
(2)
c. Oven dried
The peeled epicarp were dried in an oven with forced air
circulation (Marconi MA03515, Piracicaba, BR) at 50oC
for 54h. The dried peeled were then crushed in knife mill
type (Marconi M340 Piracicaba, BR) and kept in sealed
plastic bags in a frost free freezer (BVR 28 GBBNA
BRASTEMP, Joinville, BR) at -22oC until its use.
d. Moisture content determination
Thermal drying method was used in the determination of
moisture content of the samples.100g of sample were
placed in oven at 105± 30C and allowed to dry to a
constant weight for 24 hours (Lagha-Benamrouche, S.
and Madani, K., 2013). The moisture content (MC) was
calculated by expressing the weight loss upon drying a
fraction of the initial weight of sample used. The moisture
content of the seeds was determined by gravimetric
method which determines the mass loss from the sample
by drying to constant weight (ASABE STANDARDS,
1993 and AOAC, 2000).
(3)
(4)
Where is weight of empty crucible
is weight of crucible plus sample before drying
is weight of crucible plus sample after drying
DM is dry matter and
MC is the moisture content
e. Bulk density
The bulk density was determined using the mass to
volume ratio. The volume was determined by water
displacement method as described by Archimmedes law
of floatation. True or real density is the mass of the
sample divided by volume and can be calculated using the
equation (5):
(5)
Where,
Pr(kg/m3) = True density
M (kg) =dry specimen mass 0f 300g
V(m3) =Volume of sample = Volume of water displaced
by 300g when immersed in water (Archimedes Principle
of Floatation.)
f. Relative density
The relative density was determined for the dried sample
of sweet orange. A fixed bed of 300 cm3(extractant) was
used as standard volume of the container and the mass
was measured in a previously weighed beaker. No
separate manual compaction of sample was done. The
bulk density was then calculated from the mass of the
sweet orange peels and the volume of the container
(Saciliket al., 2003).
g. Particle Size analysis of the milled Sweet orange peels
Particle size analysis was carried out on the milled peels
product from the knife edge mill after comminution. 200g
sample was put into a stack employing a seven-frills set of
the standard tyler series of size 10-65 mesh and un shaker
screens magnetic type (Bertel, Caieiras, Brazil) which
help to promote sufficient granulometric distribution of
particles. Mass retained (MR) on each sieve sequel to
shaking were retrieved. MR (g) is % of material retained
(6)
Where MR (D) is mass of material retained in percent
is mass of material retained
The milled peels size (200 g) was determined in a vertical
vibrator sieve shaker Tyler series system (Model 1868
Bertel, Caieiras, BR) with sequential openings of 10, 14,
20, 28, 35, 48, and 65 mesh. The mean particle diameter
was determined using the method of ASAE S319.4
(ASAE, 2008) for granulometry.
The diameter measurement of the particles of Orange
peels was determined in terms of geometric mean
diameter (or median size), geometric standard deviation
of log-normal distribution by mass in ten- based
logarithm, and geometric standard deviation by mass
(ASABE STANDARDS, 2008), A mass retained in
cadapeneira was weighed in semi-analytical balance (the
5500 Mars, Sao Paulo, Brazil) and the average diameter
of the particles was calculated by the equation
(7)
(8)
(9)
Where is nominal sieve aperture size of the ith sieve,
(mm)
is nominal sieve aperture size in next larger than ith
sieve (just above the set ), (mm)
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-4, July-Aug- 2017
http://dx.doi.org/10.22161/ijeab/2.4.80 ISSN: 2456-1878
www.ijeab.com Page | 2203
is geometric mean diameter or median size of
particles by mass, (mm) , or is geometric mean diameter
or median size of particles on sieve, (mm) or is
( , which is
is geometric standard deviation of log-normal
distribution by mass in ten-based logarithm,
(dimensionless)
is geometric standard deviation of log-normal
distribution by mass in natural logarithm, (dimensionless)
is geometric standard deviation of particle by mass
,(mm)
mass of material retained on the i-th sieve (g)
N is number of sieves +1 (pan
h. Proximate analysis
The proximate compositions of the dried sample were
determined using standard methods to know the nutritive
properties. All measurements were done in duplicates and
values were presented in percentage.
i. Ash content determination
(10)
ii. Fat content determination
(11)
iii. Fibre content determination
(12)
iv. Protein determination
Protein content of the sample was determined
using the Kjeldahl method
v. Carbohydrate determination
(13)
III. RESULTS AND DISCUSSIONS
3.1 Physical Properties of the Citrus Species
Physical properties are important in many problems
associated with the design of machines and the analysis of
the behaviour of the product during agricultural
processing operations such as extraction of
phytochemicals. The summary of the result for all the
physical parameters measured were, collated, analysed
and presented (Table 1).
Table.1: Descriptive statistics of sweet orange from Nigeria.
Citrus species
Sweet orange Nig.
Property
Max
Min
mean ± St.dev
Total mass (g)
313
202.72
250.05±27.10
Mass of fruit (g)
280.18
177.26
213.10±22.26
Mass of peel(g)
55.23
73.96
32.69±7.90
Total volume (cm3)
240
85
149.43±39.30
volume of fruit (cm3)
190
64
112.25±31.56
Volume of peels (cm3)
65
12
37.18±13.88
Bulk density of peel (gcm-3)
2.24
0.085
0.99±0.38
Relative density of dried peels (gcm-3)
0.4007±0.0023
The mass of orange ranges from 202.72 - 3132 g with
average mass of 250.05 g Mass of orange peels ranges
from 73.96 - 55.23 g with average mass of 32.69 g for
Nigeria orange. Citrus fruits contains pulp, peels, internal
tissues and seeds. Citrus pulp is the solid residue that
remains after fresh fruits are squeezed for their juice. It
amounts to 50 – 70% of the fresh weight of original fruit,
contains peels 30 – 45%, internal tissues of 20 – 35% and
seeds 0 – 10%. The result obtained from the peels were
lower than the result reported by Sharma et al, (2017) of
50% of citrus peels.
The bulk density was determined using the mass to
volume. Natural bulk density of sweet orange was 0.99
gcm-3 and mean relative density obtained was 0.4007 ±
0.0023 gcm-3 for the dried milled sweet orange peels.
The rinds (peels) obtained from the pericarp of citrus is
the primary waste and is available in large quantities
during the citrus season thereby constituting
environmental hazard and pollution to the environment.
There is therefore an urgent need to put it into productive
use. Figure 1 shows the result of dried orange milled peels
from sweet orange.
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-4, July-Aug- 2017
http://dx.doi.org/10.22161/ijeab/2.4.80 ISSN: 2456-1878
www.ijeab.com Page | 2204
Fig.1: Mass Ground sweet orange peels retained in the sieves
3.2 Granulometry.
The milled peels size were determined in a vertical
vibrator with six series tyler sieve shaker Tyler series
system (Model 1868 Bertel, Caieiras, BR) with sequential
openings of 10, 14, 20, 28, 35, 48, and 65 mesh with
retained percentage mass of 2.62, 30.73, 32.53, 7.21,
18.59, 5.50 and 2.82 % respectively. The calculated
average particle diameter is 0.84 mm using equation (7).
3.3 Nutrient composition of sweet orange (Citrus
Sinensis) rinds
The result of Nutrient composition of dried milled sweet
orange peels using proximate analysis is shown in Figure
2.The nutritive composition of sweet orange peels shows
crude protein of 7.15% and crude fibre of 12.7% (Figure
2). The result of crude protein indicating that they could
serves as very high protein supplements in addition to
contributing to the formation of hormones which controls
a variety of body functions such as growth, repair and
maintenance of body protein.
Fig.2: Nutrient composition of sweet ornage (Citrus Sinensis) rind (dry matter basis)
The crude fibre was 12.79 % which also have high value
of dietary fibre and higher than the value of water leaf
(Talinumtriangulare) of 12% as reported by Aja et al,
2010. It is also higher than the crude fibre of red bell
pepper of 7.4% as reported by Odewole and Olaniyan,
(2016). The result of the crude protein of 7.4% is higher
than the crude protein reported by Awogbemi and
Ogunleye (2009) of Fluted pumpkin
(Telfairiaoccidentalis) of 2.3%. The result from the
nutritive composition showed sweet orange as a
promising source of proteins and crude fibre. The average
daily requirement of dietary fibre is 21–25 g per day for
women and 30–38 g per day for men (Food and Nutrition
Board, Institute of Medicine, 2001).Nassaret al. (2008)
suggested that 15 % of orange peel and pulp could be
incorporated as an ingredient in making biscuits, as they
are a suitable source of dietary fibre with associated
bioactive compounds (flavonoids, carotenoids etc.).It also
contains a variety of other nutrients such as proteins,
crude fibre and some minerals.
IV. CONCLUSION
In this study some physical properties and chemical
characteristics of sweet orange peels were determined. It
showed sweet orange rinds as a primary waste. The study
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-4, July-Aug- 2017
http://dx.doi.org/10.22161/ijeab/2.4.80 ISSN: 2456-1878
www.ijeab.com Page | 2205
provided relevant data which are required for the design
of processing equipment for sweet orange rinds.
Based on the chemical composition of sweet orange rinds,
the crude fibre and protein of sweet orange rinds can
serve as non-caloric bulking agents. They are also capable
of offering significant low-cost nutritional dietary
supplement to livestock and human beings. Sweet orange
rinds could be incorporated as an ingredient in processing
of foods and in livestock feeds. These uses will promote
sustainable disposal of sweet orange rinds residues.
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