Preliminary Studies on the Characterization of Orange Seed and Pawpaw Seed Oils
This study was carried out to determine the physicochemical properties of seeds and oil extracted from both papaya and orange seeds. The seeds of papaya and orange are generally discarded. However, in order to make a more efficient use of papaya and orange, it is worth investigating the use of the seeds as a source of oil. The seeds were collected from homes and the oils obtained by solvent extraction were analysed for pH, moisture content, specific gravity, refractive index, saponification value, free fatty acid, acid value, iodine value and peroxide value. The orange seed cake was analysed for sodium, potassium, calcium, magnesium, iron, zinc, copper, nitrogen and crude protein. Results showed that the oil content of the pawpaw seeds was 25.8% while that of the orange seeds was 34%. Crude protein of the orange seed was 43.72%, which was higher than that of established high protein seeds and nuts. The orange seeds had higher yield of oil than the pawpaw seeds and the nutritive content of the orange seeds makes it suitable as feed for animals. However, the acid value for pawpaw seed oil was 47.12 while that of orange seed oil was 51.40. With respect to the acid value, the oil from pawpaw seed might be better oil. However, both oils still need to be refined before they are utilized.
Received: August 29, 2010;
Accepted: December 06, 2010;
Published: January 29, 2011
Orange is from the citrus family, the fruit size varies with cultivar and crop
load, but most often measures between 2.5-4 inches in diameter. The shape of
the fruit is spherical to oblong, with a peel thickness between that of grape
fruit and tangerine and is either smooth or roughly pebbly. The presence and
amount of seed, depends also on the cultivar (Nwobi et
al., 2006). Papaya (Carica papaya L.) is a plant that grows wild
in many parts of the tropics. Papaya is important for its fruit and it is cultivated
mainly for this purpose (Puangsri et al., 2005).
It varies in size, most are oblong, globular or round, often five angled and
narrowed at the tip. The inside hollow of the fruit is lined with numerous dark
grey seeds. The seeds of papaya and orange fruits are generally discarded. However,
in order to make a more efficient use of papaya and orange, it is worth investigating
the use of the seeds as a source of oil. The extraction and use of vegetable
oils has for centuries played an important role in the manufacture of a large
number of industrial products and food items (Puangsri
et al., 2005).
Kar and Mital (1999) reported that shea butter is a
natural fat obtained from the seeds of the shea tree Butyrespermum parkii.
The shea butter fat was extracted from the seeds with various organic solvents,
namely petroleum ether, n-hexane, chloroform and benzene. It was concluded that
these solvents, particularly petroleum ether and n hexane, could be used for
the extraction of shea butter that is free from any oxidized fat and colouring
impurities. Akpan et al. (1999) carried out extraction,
characterization and modification of castor seed oil and reported that tested
parameters which include specific gravity, refractive index, acid value, saponifiation
value and iodine value for both crude and refined castor oil produced were of
good quality. In fact the iodine value obtained (84.8) for the refined oil indicates
that the oil could certainly be used as a lubricant, hydraulic brake fluid and
protecting coatings (Kyari, 2008).
Oil yielding crop plants are actually very important for economic growth of
agricultural sector. The oilseeds containing unusual fatty acids are very important
for industry; they can be used in pharmaceuticals, cosmetics, detergents, soaps,
textiles, surfactants (Hosamani and Sattigeri, 2000).
On the other hand, no oil from a single source has been found to be suitable
for all purposes because oils from different sources generally differ in their
composition. This requires the search for new sources of novel oils. Several
plants are now growing, not only for food and fodder, but also for a striking
range of products with an industrial application (Miladi
et al., 2007).
The extraction and commercialization of these oils will reasonably enhance
the profit status of most fruit juice making industries and encourage the sustenance
of the cultivation of the seedy species of sweet orange fruits. The extraction
and characterization of oils from fruit seeds have been carried out extensively,
but not much data is available on the physio-chemical properties of the oil
from the seed of African sweet orange, despite an initial attempt by some authors
who worked on the seeds of orange and closely related lime seeds (Nwobi
et al., 2006). The chemical composition of the oil extract consequently
gives a qualitative identification of oils and is a very important area in the
selective application guide for the commercialization and utility of oil products.
Fats and oils are also very important indigenous raw materials for many edibles
and non-edible purposes (Abbas Ali et al., 2008).
Thus, the aim of this study was to determine the nutritive value of orange seed
and compare the physicochemical properties of oils extracted from both papaya
and orange seeds.
MATERIALS AND METHODS
The orange seeds and pawpaw seeds were collected from homes within the University
of Nigeria Nsukka in 2007 and weighed, sun dried, deshelled and ground into
Oil extraction: The fine flour of the two different seeds was subjected
individually to solvent extraction for 5 h with petroleum spirit between 60-80°C
and then 40-60°C using soxhlet extraction method (Nwobi
et al., 2006). It was observed that the oil was more extracted at 40-60°C
than at 60-80°C.
Physico-chemical analysis: pH was determined using a Hanna pH meter
model No. 02895 (Okoye and Ibeto, 2010). Moisture content
was determined by oven dry method. Specific gravity was determined using a Hydrometer
(Gerpen et al., 2004). Refractive index was determined
using a refractometer. Nitrogen and crude protein were determined by Kedhal
method (Nzikou et al., 2007). The determination
of saponification values and Free Fatty Acid (FFA) contents were carried out
using the methods of Palm Oil Research Institute of Malaysia (Anonymous,
1995). While acid, iodine and peroxide values were determined according
to FAO (1991).
Two grams of the dried sample of the orange cake from the flour of which oil
had been extracted were prepared for determination of heavy metals by wet digestion
using 6ml perchloric acid and 12 mL nitric acid (Okoye and
Ibeto, 2010). Sodium and potassium were determined by flame photometry using
a Gallenkamp flame analyzer, calcium and magnesium were determined by EDTA titrimetry
while iron, zinc and copper were determined by atomic absorption spectrophotometry
using Alpha 4 Serial No 4200 with air acetylene flame (Okoye
and Ibeto, 2010).
RESULTS AND DISCUSSION
As shown in Table 1 and 2, the oil content
of the pawpaw seeds was 25.8% while that of the orange seeds was 34%. The moisture
content of the pawpaw seed oil was 0.18% while that of the orange seed oil was
6.43%. The moisture content of the orange seed oil was higher than 4.91% which
was obtained by Taiwo et al. (2008) in their
analysis of water melon seed oil. This might have been as a result of the difference
in chemical composition of the two fruits, age and time of harvest. However,
this is advantageous in terms of shelf life of the seed, with less moisture
content, as seeds can be preserved for a longer period. Specific gravity for
the pawpaw seed was 0.85 and this is very close to the values 0.89-0.92 g mL-1
reported for edible oils (Odufoye, 1998). The refractive
index (1.47) of the pawpaw seed oil in this study falls within values reported
for other seed oils i.e 1.48 for Teleferia occidental seed oil, 1.47 for soybean
and 1.47 for corn (Sodeke, 2005). This indicates that
the oil analysed in this study is less thick compared to most drying oils with
refractive indices between 1.48 and 1.49 (Oluba et al.,
The Iodine value of the pawpaw seed oil was 30.20, which is low. As with iodine
value content around 112, oil could be utilized for cooking and may find application
as a raw material in industries for the manufacture of vegetable oil-based ice-cream
(Nzikou et al., 2007). Free Fatty Acid (FFA)
concentration of the orange seed oil (25.70%) was far above the maximum limit
of 2.0% reported for high-grade Codex Alimentarius (Codex
Alimentairus Commission, 1993), even though the peroxide value was as low
as 0.3. Oils having high percentages of peroxide are unstable and grow rancid
easily (an unpleasant odor) (Nzikou et al., 2007).
|| Results of the analysis of pawpaw seed oil
||Results of the analysis of Orange seed oil
||Results of the analysis of Orange seed cake
|Nd means not detectable
Saponification value is used in checking adulteration. Saponification value
for the pawpaw seed oil was 79.38 while that for the orange seed oil was 194.25.
The high saponification value of the orange seed oil indicates the presence
of high percentage of fatty acids in the oil (Omolara and
Dosumu, 2009). The saponification value is in good agreement with 190.34
for Psophocarpus tetragonolobus seed oil (Abbas Ali
et al., 2008). The relatively high value recorded is indicative that
it has potential for use in the industry (Akubugwo and Ugbogu,
Acid number measures the presence of corrosive free fatty acids and oxidation
products. This is actually an important variable in considering the quality
of oil because the lower the free fatty acid, the better the quality of oil.
The acid value for pawpaw seed oil was 47.12 while that of orange seed oil was
51.40 which are both far above the acceptable limits for edible oils ≤10
(Balley, 1982). With respect to the acid value, the oil
from pawpaw seed might be better oil. However, both oils still need to be refined
before they are utilized.
As shown in Table 3, the orange seeds had 0.02 and 7.33 ppm
of sodium and potassium, respectively. This were far lower than what was obtained
by Omode et al. (1995) in their analysis of oil
seeds having high concentrations of potassium (265±2.1 to 1050±4.2%)
and sodium (100±1.4 to 260±1.4%). Zinc was not detected while
other elements were also found at relatively low concentrations e.g., concentrations
copper, iron and calcium were 0.01, 0.02 and 0.06 ppm, respectively. However,
crude protein of the orange seed was 43.72% which was higher than that of established
high protein seeds and nuts like cowpea (22.7%) and soybeans (35%) (Taiwo
et al., 2008).
The orange seeds had higher yield of oil than the pawpaw seeds and the high
protein content of the orange seeds makes it suitable as feed for animals. The
utilization of the orange seed will not only be a good avenue of controlling
the indiscriminate disposal of these seeds in the environment but will also
be economically valuable as animal feed.
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