This paper performed the physicochemical and proximate analysis of the extracts isolated from Citrus sinensis from Dutsinma local government area of Katsina state in Nigeria. Characteristics of the seeds were investigated by Association of Official Analytical Chemists (AOACs). The seeds were found to be potential raw materials for livestocks nutrition, cosmetic manufacturing and construction industries. The physicochemical parameters included oil percentage yield, melting point, specific gravity, iodine value, saponification value, peroxide value, free fatty acid value, and acid value. The proximate parameters included moisture, protein, carbohydrate, crude fiber, and ash content. This study concluded that Citrus sinensis seed could be utilized as potential raw material for oil producing industries.
Concern continues to grow as to insufficient supply of fat in the diet of an average Nigerian (FAO, 1992) [
This work aimed to investigate the proximate and phytochemical properties of extracts from Citrus sinensis residues given their economic and commercial potential, assess the quality of the oil and cake so extracted and determine the industry best suited for their use.
All reagents used for this study were pure and of analytical grade.
To this end, five kilograms of residues of Citrus sinensis were handpicked by the Department of Agroforestry of the Katsina state Ministry of Environment from residues from a gallery forest of orange trees in April 2015 after identification and characterization of the trees by a plant scientist from Musa Yar’adua University, Katsina.
The usable residues were scavenged de-shelled, washed and well dried under room temperature for two weeks prior to pulverization which is the last preparation stage with the aid of a blending machine and stored in a container for further use.
Physicochemical properties
Further on in this study, we investigated the presence of physico-chemical components in the oil extracts and carefully evaluated proximate properties in accordance with the following principles and protocols.
Determination of oil yield
The total amount of the oil extracted from residues was determined by using the equation:
W1: Weight of the flask alone;
W2: Weight of flask and oil;
W3: Actual weight of residues from Citrus sinensis used (Nwokonkwo, 2013) [
Determination of melting point
1 cm3 of Citrus sinensis residues oil was introduced into a capillary tube and frozen and allowed to stand at room temperature until the oil melted at temperature that was recorded as the melting point.
Determination of specific gravity [
The specific gravity was determined by weighing an empty 25 cm3 density bottle. The bottle was filled to mark with oil and weighed thereafter. The same experiment was carried out by filling the same density bottle to mark with distilled water after washing and rincing it with distilled water.
The specific gravity was then derived using the following equation
W1: Weight of oil;
W2: Weight of distilled water [
Saponification value determination
Saponification value was determined following the protocol prescribed by AOAC (2009) [
Iodine value is a measure of degree of unsaturation defined as grams of iodine absorbed per 100 grams of sample. This value was determined in accordance with the AOAC [
Acid value reflects the amount of fatty acids hydrolyzed from tryacylglycerols.
This value was determined by adding to oil sample 100 ml 95% neutralized ethanol and 2 ml phenolphthalein indicator. After shaking for the mixture to dissolve, titration follows using 0.1 N NaOH and shaking vigorously until the endpoint is reached. This is indicated by a slight pink color that persists for 30 seconds AOACs (2009) [
-Peroxide value estimation
Peroxide is defined as the milliequivalent of peroxide per kilogram of fat as determined in a titration procedure to measure the amount of peroxide or hydroperoxide groups.
Peroxide value was estimated in accordance with the following procedure, as prescribed by AOAC [
-Proximate composition determination
An empty crucible was cleaned and dried in an oven and then filled with two grams (2 g) of pulverized sample in the same oven at 105˚ until a constant weight is attained. The moisture content was calculated as a loss in weight of the original sample and expressed in percentage of moisture content (FAO, 2004; Udeme et al., 2013) [
Determination of crude protein
Crude protein in the pulverized seeds residues was determined using Kjeldahl method with some changes. 0.5 grams of pulverized residues were digested with 5 mls of concentrated sulfuric acid in the presence of Kjeldahl catalyst. The nitrogen from protein in the sample was converted into ammonium sulfate that reacted with 2.5 mls of 2.5% Brucine reagent, made up of 5 mls 98% sulfuric acid to give a colored derivative with the absorbance determined at 470 nm. The percentage nitrogen was then calculated and multiplied by 6.25 to obtain the crude protein [
Estimation of crude lipid from residues
This estimation was executed using Soxhlet extraction method. Two (2) grams of powdery form of residues were weighed, wrapped in a filter paper and placed in a thimble, covered with cotton wool and placed in an extraction column connected to a condenser. 40 mls of n- hexane were used to extract crude lipids [
Determination of crude fiber from residues [
This was achieved by using AOAC method. Five (5) grams of pulverized residues and 200 mls of 1.25% H2SO4 were heated for thirty (30) minutes and filtered with a Buchner funnel the remainder was washed with distilled water until it is acid free. 200 mls of 1.25% NaOH was also boiled along with the same remainder for thirty (30) minutes. The mixture was also filtered and washed several timesa until it was alkaline free. It was then rince with 10% HCl once and twice with ethanol. At the end of the protocol, the remainder was rinsed with petroleum ether three (3) times, put in a crucible and dried at 105˚C in an oven all through the night. After cooling in a dessicator, the remainder was ignited in a muffle furnace at 550˚C for ninety (90) minutes to obtain the weight of the ash.
Determination of ash content from residues
In accordance with the method of AOAC [
Carbohydrate determination from residues
The carbohydrate content was determined by subtracting the summed up percentage composition of moisture, protein, lipid, fiber and ash content from 100 [
The results of physicochemical and proximate analyses were expressed as means ± standard error.
The physicochemical analyses of oil from residues revealed the following results (
Proximate analysis showed the following results.
The proximate parameters in pulverized residues were tabulated (
Properties | Values |
---|---|
Oil percentage yield | 36 ± 0.05 |
Melting Point | 9.920 ± 0.020 |
Specific gravity | 0.916 ± 0.010 |
Saponification value | 198 ± 0.020 |
Iodine Value | 118 ± 0.001 |
Peroxide Value | 18.8 ± 0.010 |
Free Fatty acids | 3.1 ± 0.020 |
Acid Value | 1.3 ± 0.050 |
Nutrients | Values in percentage |
---|---|
Moisture | 2.4 ± 0.002 |
Protein | 4.82 ± 0.015 |
Carbohydrate | 7.6 ± 0.001 |
Crude fiber | 19.70 ± 0.010 |
Ash | 14.76 ± 0.001 |
The chemical characteristics of Citrus sinensis seeds oil were evaluated by the following parameters, acid, iodine, saponification, specific gravity, melting point, free fatty acids and percentage oil yield as presented in
The percentage oil yield of 36 was higher than 27.845 reported for Cussonia batery by Nwokonkwo (2013) [
The saponification value of 198 mg KOH/g of oil obtained from Citrus sinensis seeds agrees with values for most vegetable oils ranging from 188 - 253 mg KOH/g (Oluba et al., 2008; Otasie and Akinhanmi, 2009; Nwokonkwo, 2013) [
The percentage protein for instance of 4.82% is far below 16% - 17% reported as best for rabbit performance in tropical environment (Anugwa et al., 1982; Aduku and Olukosi, 1990) [
The crude fiber of 19.70% may not facilitate nutrient digestibility, in line with the findings of Adegbola and Okonkwo (2002) [
Physicichemical and proximate analysis of extracts from residues of Citrus sinensis from Dutsinma Local Government Area of Katsina State in Nigeria shows great nutritional attributes and makes Citrus sinensis a potential raw material for cosmetic, construction and livestock food industries. The use of these seeds will greatly abate global warming by mitigating environmental pollution caused by their decomposition to a minimal level. However, further research is recommended on Citrus sinensis seeds employing specific enzymes (Victor Markus et al., 2014) [
Gnimintakpa Joseph,Sa’ada Abdullahi, (2016) Physicochemical and Proximate Analysis of Extracts from Citrus sinensis of Dutsinma, Katsina State, Nigeria. Open Access Library Journal,03,1-7. doi: 10.4236/oalib.1102495