Physiochemical Parameters of Extracted Castor Oil in Saudi Arabia

Objectives: This study aimed at the extraction and characterization of castor seed oil purchased from local market in Riyadh, Saudi Arabia. Methods: Castor oil was extracted from beans via extraction with n-hexane by using Soxhlet apparatus. The oil was subjected to different test for characterizations. Results: A positive test with the disappearance of the purple color of KMnO4 indicated the presence of double bond. Also the reaction of the oil with concentrated H2SO4 giving reddish brown color, has confirmed the presence of double bond. The physiochemical parameters were carried out by simple reaction and the result has showed that the color of the oil is pale yellow color, the density is 1.01 g/mL, peroxide value is 12.8 Meq/K, acid number is 0.6288 mg KOH/g and saponification value is 171.105 mg/g. Conclusion: The studied castor seeds contain a high percentage of oil, which is rich in unsaturated oil.


INTRODUCTION
Castor oil is one of the few naturally occurring triglycerides that approach being a pure compound, since the fatty acid portion is nearly nine-tenths ricinoleic 1 .Its crude form is a pale straw colour that turns colorless or slightly yellowish after refining and bleaching.Castor oil pale amber viscous liquid derived from the seeds of the plant Ricinus communis is sometimes known as ricinus oil 2 .Castor plant, Ricinus communis L. is a species of flowering plant in the Spurge family (Euphorbiaceae), which contains a vast number of plants mostly native to the tropics 2 .Ricinus communis L belongs to a monotypic genus Ricinus, which is a latin word named for tick 2 .The crude oil has a distinct odor, however, it can easily be deodorized in the refining process like any other vegetable oils.It contains triglycerides, which chemically is a glycerol molecule with each of the three hydroxyl groups esterified with long chain fatty acids.Their major fatty acids are of the unsaturated fatty acids, hydroxylated 12-hydroxy, 9-octadecenic acid, known familiarly as the ricinoleic acid 3 , containing between 87-90% ricinoleic acid 5,6 .The presence of a hydroxyl group at C12 of the recinoleic acid, the ester linkages, double bonds and hydroxyl groups provide reaction sites that makes it usually polar, which provide sites for the production of a wide range of natural and synthetic resins, waxes, polymers and elastomers.It also has excellent emollient and lubricating properties, a marked ability to wet and disperse dyes, pigments and fillers 7 as well as several medicinal values 8 .Castor oil has excellent solubility in methanol and hence theoretically an ideal oil for trans-esterification to biodiesel, requiring a minimum amount of catalyst and

MATERIALS AND METHODS
Caster seeds were purchased from local herbs market (Whatcom Seed Company®) (seedrack.com) in Riyadh.The seeds were collected and the damaged seeds were discarded.The seeds were cleaned, de-shelled and dried at room temperature for 48 hours.All chemicals used in the study were analytical grade and used without further purification.

Extraction of oil
To 300 ml of n-hexane (in round bottom flask), 100 g of caster seeds were placed in the thimble and was inserted in the center of the extractor.The Soxhlet set up was heated at 60 ºC and allowed to continue for 6 hours.Then cooled to room temperate and dried under vacuum the extracted oil was collected as pale yellow oil 3 (20 g, 20%).

Acid value
Ten g of castor oil was weighted by using digital balance in a clean conical flack, then 25 ml of diethyl ether and 25 ml of ethanol were mixed in a 250 ml beaker then added to conical flack contents then few drops of phenolphthalein were added to the mixture.The mixture was titrated against 0.1 M NaOH to the end point.The experiment was repeated three times 10 .

Peroxide value
Five g of castor oil was weighed in a clean conical flack, 12 ml of chloroform was added and shacked well, then 18 ml of acetic acid (CH3COOH) was added, followed by 0.5 mL of potassium iodide (Kl) the flack content was shaked well and then titrated against/ sodium thiosulfate (Na2S2O3) until the end point.The experiment repeated three times 10 .

Saponification value
Two g of castor oil was weighted by using digital balance in conical flack, 25 ml of 0.5 N alcoholic potassium hydroxide (KOH) was added to conical flack.The mixture was refluxed on water bath for 30 min.Then titrated with 0.5 M Hydrochloric acid (HCl) and using phenolphthalein as an indicator, until the end point.The blank test conducted by repeated the same experiment without the addition of the oil 10 .

Moisture and volatilities
Five g of seeds was weighted in porcelain crucibles and kept in hot air oven at 110 ºC for 4 h.The weight was taken after cooling to room temperature 11 .Moisture = W1/W2 * 100 Where, W1: weight of sample before heating; W2: weight of sample after heating.

Density of oil
One ml of oil was measured by measurement cylinder and the weight of this amount was taken 12 .D = M/V Where, M: weight of sample in gram; V: volume of sample in ml.

Reaction with potassium permanganate
Few drops of potassium permanganate (KMnO4) were added to 1 ml of oil and were shaked well.The potassium permanganate color disappeared 13 .

Reaction with sulfuric acid
Few drops of sulfuric acid (H2SO4) were added to 1ml of oil, the solution became dark 13 .

RESULTS AND DISCUSSION
Castor oil was evaluated for physical and chemical properties as shown in Table 1, the density 1.01 g/ml and the moisture and volatilities 5%.The saponification value of castor seeds oil was found to be 171.105%mg/g, the peroxide value 12.8 Meq/kg and the acid value is 0.6288 mg NaOH/g.A potassium permanganate (KMnO4) Solution can oxidize a double bond at room temperature to form a 1,2diol with the simultaneous reduction of Mn +7 in KMnO4) to Mn +4 in manganese oxide (MnO2).
A positive test is the disappearance of the purple KMnO4 and the appearance of MnO2 as brown precipitate.A potassium permanganate (KMnO4) Solution can oxidize a double bond at room temperature to form a 1,2-diol with the simultaneous reduction of Mn +7 in (KMnO4) to Mn +4 in manganese oxide (MnO2).

CONCLUSION
In conclusion, based on the above data, castor seeds contain a high percentage of oil showing their composition is rich in unsaturated oil.