A COMPARISON OF IODINE VALUES OF SOME COMMON VEGETABLE OILS

9

Pie Chart Showing the iodine values of five vegetable oils
A COMPARISON OF IODINE VALUES OF SOME COMMON VEGETABLE OILS



BY



CHRISTOPHER, UNYIME EBONG
UG/011/2501



DEPARTMENT OF CHEMICAL SCIENCES,
FACULTY OF SCIENCE,
NIGER DELTA UNIVERSITY,
WILBERFORCE ISLAND,
BAYELSA STATE.




OCTOBER, 2015.
A COMPARISON OF IODINE VALUES OF SOME COMMON VEGETABLE OILS




BY



CHRISTOPHER, UNYIME EBONG



ABSTRACT
Vegetable oils are triglycerides extract from plants and made of up of fatty acid chains. The fatty acids can be saturated or unsaturated depending on the number of carbon-carbon double bonds. The degree of saturation/unsaturation is indicated by the iodine value of the oil. Hence this research work was aimed at comparing the iodine values of five different vegetable oil (groundnut oil, palm oil, olive oil, palm kernel oil and coconut oil) samples bought from Swali market, Yenagoa, Bayelsa state in Nigeria. The vegetable oils were analyzed for their iodine values and the following results were obtained: For groundnut oil, the iodine values were found to be 86.00 g I2/100g, olive oil 81.01 g I2/100g, palm oil 53.91 g I2/100g, palm kernel oil 36.74 g I2/100g, and coconut oil 10 g I2/100g. The iodine values of the five vegetable oil samples analyzed follows the order: Groundnut oil > Olive oil > Palm oil > Palm kernel oil > Coconut oil. Since their iodine values are lower than 100, they are considered to be a non-drying oil which does not harden when it is exposed to air and therefore can be used industrially for the production of hard soaps and are of good nutritional value, hence the oils pose no significant health risks to consumers. Thus, the result of these findings shows that the iodine values obtained were within the regulatory standard and did not exceed the permissible level.
















TABLE OF CONTENT






















CHAPTER ONE
Introduction
Vegetables oils are derived from plant sources like soya beans, melon, groundnut, corn, oil palm, shea butter, coconut, etc. The term "vegetable oil" can be narrowly defined as referring only to substances that are liquid at room temperature (Odoemelam, 2005), or broadly defined without regard to a substance's state of matter at a given temperature (Barku, et al., 2012). For this reason, vegetable oils that are solid at room temperature are sometimes called vegetable fats. Some of these vegetable oils are used for domestic (edible) and industrial purposes (Tautorus, 2006).
The domestic use of vegetable oil began in the early 1900s when new chemical processes allowed them to be extracted. Unlike butter or coconut oil, these vegetable oils can not be extracted just by pressing or separating naturally, they must be chemically removed, deodorized and altered. Vegetable oils are composed of triglycerides which are the ester of one molecule of glycerol and three molecules of fatty acids. Fatty acids are primary nutritional components found in edible seed oils.
Vegetable oils are mainly classed as Oleic-Linoleic acid oils since they contain a relatively high proportion of unsaturated fatty acids, such as the monounsaturated oleic acid and the polyunsaturated linoleic acid (Nkafamiya, et al., 2010; Musa, et al., 2012). They are characterized by a higher ratio of polyunsaturated fatty acids to saturated fatty acids. Vegetable oils contain a very high concentration of Omega 6 fatty acids and polyunsaturated fats.
Nutritionally, vegetable oils are usually preferred to animal fat as evidence linking health benefits to the consumption of vegetable oils continues to grow (Parry, et al., 2005) even when recent researches (Wallstrom, et al., 2007; Crowe, et al., 2008; Sieri, et al., 2008; Alexander, et al., 2009) disapproves this notion. Vegetable oils also contain additional health beneficial phytochemicals such as saponin, phlobatanin, flavonoid, tanin, terpenoid, anthraquinone, etc. Majority of the phytochemicals have been known to bear valuable therapeutic activities such as insecticidals (Kambu, et al., 1982), antibacterial, antifungal (Lemos, et al., 1990), anticonstipative, spasmolytic (Sontos, et al., 1998), antiplasmodial (Benoitvical, et al., 2001) and antioxidant (Vardar-unlu, et al., 2003) activities etc. Vegetable oils also contain some metals; some of these metals like Na, K, Ca, Mg, Fe, Cu, Zn and Mn are essential nutrients for human growth while certain forms of these metals can be toxic. The presence of trace metals is an important factor as far as the quality of edible oil is concerned.
Vegetable oils are a very important ingredient in many manufactured products. Vegetable oils are used in various industrial applications such as emulsifiers, lubricants, plasticizers, surfactants, plastics, solvents, and resins. Vegetable oils are reusable. They are used for animal feed and pet food. More recently, waste vegetable oils have become known for their ability to be refined into biodiesel, which can be used like conventional diesel fuel in diesel engines. Vegetable and edible oils had made an important contribution to the diet of people in many countries, serving as a good source of protein, lipid and fatty acids for human nutrition including the repair of worn out tissues, new cells formation as well as a useful source of energy (Trease, and Evans, 2005).
In Nigeria, the major sources of edible oils are groundnut, palm and coconut. Vegetable oils, mostly groundnut oil is of high quality and can withstand higher temperature without burning or breaking down. It has neutral flavour and odour. It does not absorb odours from other foods (Passera, 2008; Musa et al., 2012). These make it the most preferred oil in most parts of Nigeria.
It is therefore necessary to analyze these vegetable oils that are preponderant in our market places to determine its edibility, suitability for a given purpose and its overall impact on public health.

Aims and Objectives
This research work is aimed at comparing the iodine values of some common vegetable oils. The specific objectives are:
To examine the iodine values of groundnut oil, palm oil, palm kernel oil, olive oil and coconut oil.
To compare the iodine values with a regulatory standard in order to ascertain their edibility and industrial applications.












CHAPTER TWO
2.1 Literature Review
Ibrahim, et al., (2008), examined the physical and chemical characteristics of olive oils from cooperatives for olive growers in the North of Morocco. Their study were aim at evaluating the physical and chemical characteristics of olive oils (acidity, pH, peroxide values, saponification number, Iodine value of all olive oils samples ranged from (79.44 - 91.38 g of iodine/100 g oil), they were not exceeding limits that give very strong indication of degree of unstauration of a molecule, ultraviolet spectrophotometric analysis (k232 and k270), refractive index), fatty acids composition and total phenol content. The sample were also analyzed for fatty acids commonly present in olive oils which are palmitic, palmitoleic, stearic, oleic, linoleic, linolenic, and arachidic. Oliec acid were found in high percentage ranged from (64.80 to 72.80), followed by palmitic, Linoleic, palmitoleic, stearic and linolenic. Arachidic acid was detected in all olive oil samples but in low percentage. Total phenol contents expressed as gallic acid of olive oils values ranged from (112 to 313 mg/kg). All olive oil samples were compared with International Olive Oil Council (IOOC), were not exceed the limits and exhibited remarkable physicochemical properties and could be useful as edible oils and industrial applications.
Atasie and Akinhanmi, (2009) reported the extraction, compositional studies and physico-chemical characteristics of palm kernel oil. Proximate, physico-chemical and elemental analysis of palm kernel nut were determined to contain fat/oil 42%, crude protein 7.01%, moisture 6.5%, crude fibre 11.09% and carbohydrate (by difference) 33.40%. The elemental composition (mg/100 g), included: Na (37.00±0.40, K (39.51±0.22), Mg (3.60±0.1), Ca (19.0±0.42), Fe (20.04±0.28), Zn (2.82±0.30), P (3.4±0.00). The result of the physico-chemical properties of the palm kernel oil were: saponification value (234.815 mg/KOH/g), refractive index (1.435), iodine value (41.24g/100g), acid value (11.60 mg/KOH/g) and peroxide value (1.70meq/kg).
Amira, et al., (2014) investigated the physicochemical properties of palm oil and the following results were obtained: Saponification value; 280.5±56.1 mgKOH/g, acid value; 2.7±0.3 mg KOH/g, Free Fatty Acid (FFA); 1.35±0.15 KOH/g, ester value; 277.8±56.4 mgKOH/g, peroxide value; 14.3±0.8 mEq/kg; iodine value; 50.08-58.90g I2/100g, mgKOH/g, Specific Gravity (S.G) value; 0.904, refractive index; 1.412 and inorganic materials; 1.05%. Its odour and colour were heavy burnt smell and burnt brown, respectively. These values were compared with those obtained for groundnut and coconut oils. It was found that the physico-chemical properties of palm oil are comparable to those of groundnut and coconut oils except for the peroxide value (i.e., 14.3±0.8 mEq) which was not detectable in groundnut and coconut oils.
Musa, et al., (2012) examined the physicochemical properties of some commercial groundnut oil products sold in Sokoto metropolis, Northwest Nigeria. The physicochemical properties of commercial groundnut oils sold in Sokoto metropolis, Sokoto State, Northwest Nigeria were investigated in their study. Four different groundnut oil products purchased from Sokoto main market, Old market, Kara market and Mabera area within the metropolis and one extracted from groundnut seeds in the laboratory were analysed. The oil from Mabera was found to have the highest saponification value of 215.05 ± 1.36 mg KOH/g which is significantly high compared to that extracted in the laboratory (175.78 ± 0.93). Iodine value was significantly higher at (pı 0.05) in oil from the laboratory (95.87 ± 0.15 g/100 g) compared to oils from Sokoto main market (43.72 ± 0.21) and Mabera area (45.12 ±0.35). Groundnut oil from Sokoto main market has the highest acid value of 6.83 ± 0.15 which was above the cut-off value of 5.99, while the oil extracted in the laboratory has the lowest acid value of 1.88 ± 0.15. There was no significant difference at (pı 0.05) in the specific gravity of the different oil samples. The range was 0.900 – 0.918. The results show that the oils are of good nutritional value and are good for industrial applications, hence the oils pose no significant health risks to consumers in Sokoto metropolis.
Sani, et al., (2014) evaluated the physicochemical properties, phytochemicals and mineral composition of Cocosnucifera L. (Coconut) Oil. They determined the potential applications of the coconut seed by investigating the physicochemical characteristics as well as the phytochemical and mineral compositions of its extracted oil content. The oil was extracted using Soxhlet apparatus, and the physicochemical characterization, together with the phytochemical screening and determination of the mineral composition were carried out using standard methods. The physicochemical parameters of the extracted oil were as follows: acid value 0.7963± 0.21 mg KOH/g, saponification value 7.74 ± 0.73mg KOH/g, iodine value 46.8±0.63 I2/100g, free fatty acid 20.49±1.46 (% oleic acid), peroxide value (mEq H2O2/100g) 10.0 ± 5.0, specific gravity(g) 0.95.0.05. The oil was observed to have clear white appearance, liquid at room temperature and has a nutty smell when fresh and unpleasant when rancid. Cocosnucifera L. seed kernel has low oil content of 26.61%. The phytochemical analysis of the seed oil revealed the presence of saponins, alkaloids, flavonoids, steroids, and terpenoids, and absence of cardiac glycosides, tannins, phenols, phlobatanins and anthraquinones. The result of the mineral element analysis revealed that 1 L of the oil contains 3.67±0.59mg of sodium, 2.33±0.59mg of potassium, 1.50±0.03mg of calcium, 0.28±0.03mg of magnesium, 0.17±0.06mg of manganese, 0.07±0.01mg of copper, 1.70 ±0.02mg of iron, 0.33 ±0.01mg of Zinc and 0.00mg of lead. These results showed that the Cocosnucifera seed can be a good source of oil, and the extracted oil contains an appreciable amount of phytochemicals and mineral elements. Therefore, Justification of the use of the coconut oil for food, medicinal and cosmetic was expatiated
2.2 Iodine Value
The iodine value equals the number of grams of iodine required to saturate the fatty acids present in 100 grams of the oil or fat. Technically it is the value of the amount of iodine, measured in grams, absorbed by 100 grams of a given oil sample. Iodine values are often used to determine the amount of unsaturation in fatty acids. This unsaturation is in the form of double bonds, which react with iodine compounds. The higher the iodine number, the more C=C bonds are present in the fat (Mbatchou and Kosoono, 2012).

All fats and oils are composed of fat molecules known as fatty acids. The molecules can be classified into three categories depending on their degree of saturation; saturated, monounsaturated, and polyunsaturated fatty acids. No oil in nature is composed entirely of any one of these three. All dietary oils contain a mixture. Soybean oil, for example, is referred to as a polyunsaturated oil because that is the predominant fatty acid. It also contains 24 percent monounsaturated fatty acids and 15 percent saturated fatty acids. Coconut oil is also a mixture. It contains 92 percent saturated fatty acids, 6 percent monounsaturated fatty acids, and 2 percent polyunsaturated fatty acids (Akububugwo and Ugbogu, 2007).
The terms saturated, monounsaturated, and polyunsaturated refers to the degree of hydrogen saturation. A saturated fatty acid contains all the hydrogen atoms it possibly can. In other words, it is fully saturated with hydrogen. A monounsaturated fatty acid contains all but one pair of hydrogen atoms it can hold. Polyunsaturated fatty acids are lacking two or more pairs of hydrogen atoms.
A fatty acid that is missing any hydrogen atoms is classified as being unsaturated. This includes all monounsaturated and polyunsaturated fatty acids. Unsaturated fats have a lower melting point and are more likely to be liquid at room temperature this is because as you increase the number of double bonds in a fatty acid, you reduce that ability for oils to gain a conformation that would make them solid, so they remain liquid. Saturated fats have a higher melting point and are more likely to be solid at room temperature (Ramakrishna, et al., 2004).



Although the iodine value is used primarily in industry, it is of value to us because it gives an indication of the oil's stability and health properties and the higher the iodine value, the greater amount of unsaturation (Akububugwo and Ugbogu, 2007).

2.3 Vegetable Oil
Vegetable oils are triglycerides extracted from plants. Such oils have been part of human culture for millennia. Edible vegetable oils are used in food, both in cooking and as supplements. Many oils, edible and otherwise, are burned as fuel, such as in oil lamps and as a substitute for petroleum-based fuels. Some of the many other uses include wood finishing, oil painting, and skin care.
There are several types of plant oils, distinguished by the method used to extract the oil from the plant. The relevant part of the plant may be placed under pressure to extract the oil, giving an expressed (or pressed) oil. The oils included in this list are of this type. Oils may also be extracted from plants by dissolving parts of plants in water or another solvent. The solution may be separated from the plant material and concentrated, giving an extracted or leached oil. The mixture may also be separated by distilling the oil away from the plant material. Oils extracted by this latter method are called essential oils. Essential oils often have different properties and uses than pressed or leached vegetable oils. Finally, macerated oils are made by infusing parts of plants in a base oil, a process called liquid-liquid extraction.









Figure 1: Olive oil Figure 2: Palm kernel oil










Figure 3: Palm oil






Figure 4: Groundnut oil





Figure 5: Coconut oil
2.3.1 Production of Vegetable Oils
To produce vegetable oils, the oil first needs to be removed from the oil-bearing plant components, typically seeds. This can be done via mechanical extraction using an oil mill or chemical extraction using a solvent. The extracted oil can then be purified and, if required, refined or chemically altered.
2.3.2 Mechanical extraction
Oils can also be removed via mechanical extraction, termed "crushing" or "pressing." This method is typically used to produce the more traditional oils (e.g., olive, coconut etc.), and it is preferred by most health food customers in the United States and in Europe. There are several different types of mechanical extraction: expeller-pressing extraction is common, though the screw press, ram press, and Ghani (powered mortar and pestle) are also used. Oil seed presses are commonly used in developing countries, among people for whom other extraction methods would be prohibitively expensive; the Ghani is primarily used in India.
2.3.3 Solvent extraction
The processing of vegetable oil in commercial applications is commonly done by chemical extraction, using solvent extracts, which produces higher yields and is quicker and less expensive. The most common solvent is petroleum-derived hexane. This technique is used for most of the "newer" industrial oils such as soybean and corn oils. Supercritical carbon dioxide can be used as a non-toxic alternative to other solvents.
2.3.4 Sparging
In the processing of edible oils, the oil is heated under vacuum to near the smoke point, and water is introduced at the bottom of the oil. The water immediately is converted to steam, which bubbles through the oil, carrying with it any chemicals which are water-soluble. The steam sparging removes impurities that can impart unwanted flavors and odors to the oil.
2.3.5 Hydrogenation
Oils may be partially hydrogenated to produce various ingredient oils. Lightly hydrogenated oils have very similar physical characteristics to regular soya oil, but are more resistant to becoming rancid. Hardening vegetable oil is done by raising a blend of vegetable oil and a catalyst in near-vacuum to very high temperatures, and introducing hydrogen. This causes the carbon atoms of the oil to break double-bonds with other carbons, each carbon forming a new single-bond with a hydrogen atom. Adding these hydrogen atoms to the oil makes it more solid, raises the smoke point, and makes the oil more stable (AOCS. 2007). .
A simple hydrogenation reaction is: H2C=CH2+H2 CH3CH3



Hydrogenated vegetable oils differ in two major ways from other oils which are equally saturated. During hydrogenation, it is easier for hydrogen to come into contact with the fatty acids on the end of the triglyceride, and less easy for them to come into contact with the center fatty acid. This makes the resulting fat more brittle than a tropical oil; soy margarines are less "spreadable". The other difference is that trans fatty acids (often called trans fat) are formed in the hydrogenation reactor, and may amount to as much as 40 percent by weight of a partially hydrogenated oil. Hydrogenated oils, especially partially hydrogenated oils with their higher amounts of trans fatty acids are increasingly thought to be unhealthy.
Reactions of Fats and Oils
Rancidification
When oils are exposed to sunlight, photosynthesis tend to occur which is disrupted leading to release of the hydrogen ions that reacts with molecular oxygen to form loosely combined hydrogen peroxide. The unstable peroxide unites with unsaturated bond of triacylglyceride to form a glyceride peroxide which in turn splits into an aldehyde and forms the rancid compound that can be detected through sensory evidence. Three pathways for rancidification are recognized (Freeman, 2000):
Hydrolytic rancidity: Hydrolytic rancidity refers to the odor that develops when triglycerides are hydrolyzed and free fatty acids are released. This reaction of lipid with water sometimes requires a catalyst, but results in the formation of free fatty acids and salts of free fatty acids. In particular, short-chain fatty acids, such as common butter fats, are odorous. Rancidity in foods may be very slight, indicated by a loss of freshness to very severe, indicated by objectionable odors and/or flavors.
Oxidative rancidity: Oxidative rancidity is associated with the degradation by oxygen in the air. Via a free radical process, the double bonds of an unsaturated fatty acid can undergo cleavage, releasing volatile aldehydes and ketones. Oxidation primarily occurs with unsaturated fats. For example, even though meat is held under refrigeration or in a frozen state, the poly-unsaturated fat will continue to oxidize and slowly become rancid. The fat oxidation process, potentially resulting in rancidity, begins immediately after the animal is slaughtered and the muscle, intra-muscular, inter-muscular and surface fat becomes exposed to oxygen of the air. This chemical process continues during frozen storage, though more slowly at lower temperature. The process can be suppressed by the exclusion of oxygen or by the addition of antioxidants. Thus, airtight packaging will slow rancidity development.
Microbial rancidity: Microbial rancidity refers to a process in which microorganisms, such as bacteria or molds, use their enzymes such as lipases to break down fat. This pathway can be prevented by sterilization.
Consuming rancid food products is unlikely to cause immediate illness or harm. Rancidification can reduce the nutritional value of food, and some vitamins are highly sensitive to degradation. In addition, rancidification can produce potentially toxic compounds associated with long-term harmful health effects concerning advanced aging, neurological disorders, heart disease, and cancer. Hydrogenated oils have been shown to cause what is commonly termed the "double deadly effect", raising the level of low density lipoproteins (LDLs) and decreasing the level of high density lipoproteins (HDLs) in the blood, increasing the risk of blood clotting inside blood vessels. A high consumption of omega-6 polyunsaturated fatty acids (PUFAs), which are found in most types of vegetable oil (e.g. soyabean oil, corn oil– the most consumed in USA, sunflower oil, etc.) may increase the likelihood that postmenopausal women will develop breast cancer. A similar effect was observed on prostate cancer in mice. Plant based oils high in monounsaturated fatty acids, such as olive oil, peanut oil, and canola oil are relatively low in omega-6 PUFAs and can be used in place of high-polyunsaturated oils.
2.5 Uses of Triglyceride Vegetable Oil
The following are some of the uses of vegetable oils:
Culinary uses: Many vegetable oils are consumed directly, or indirectly as ingredients in food – a role that they share with some animal fats, including butter and ghee.
Industrial uses: Vegetable oils are used as an ingredient or component in many manufactured products. Many vegetable oils are used to make soaps, skin products, candles, perfumes and other personal care and cosmetic products. Some oils are particularly suitable as drying oils, and are used in making paints and other wood treatment products. Dammar oil (a mixture of linseed oil and dammar resin), for example, is used almost exclusively in treating the hulls of wooden boats. Vegetable oils are increasingly being used in the electrical industry as insulators.
Pet food additive: Vegetable oil is used in production of some pet foods. In some poorer grade pet foods though, the oil is listed only as "vegetable oil", without specifying the particular oil.
Fuel: Vegetable oils are also used to make biodiesel, which can be used like conventional diesel. Some vegetable oil blends are used in unmodified vehicles but straight vegetable oil, also known as pure plant oil, needs specially prepared vehicles.
Margarine: Margarine is a semi-solid emulsion composed mainly of vegetable fats and water. While butter is derived from milk fat, margarine is mainly derived from plant oils and fats and may contain some skimmed milk. In some locales it is colloquially referred to as oleo, short for oleomargarine. Margarine, like butter, consists of a water-in-fat emulsion, with tiny droplets of water dispersed uniformly throughout a fat phase which is in a stable crystalline form. Margarine has a minimum fat content of 80%, the same as butter, but unlike butter reduced-fat varieties of margarine can also be labelled as margarine. Margarine can be used both for spreading or for baking and cooking. It is also commonly used as an ingredient in other food products, such as pastries and cookies, for its wide range of functionalities.
Soap Industry: Soap is a salt of a fatty acid. Soaps are mainly used as surfactants for washing, bathing, cleaning, in textile spinning and are important components of lubricants. Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strongly alkaline solution. Fats and oils are composed of triglycerides; three molecules of fatty acids are attached to a single molecule of glycerol. The alkaline solution, which is often called lye, (although the term "lye soap" refers almost exclusively to soaps made with sodium hydroxide) brings about a chemical reaction known as saponification. In saponification, the fats are first hydrolyzed into free fatty acids, which then combine with the alkali to form crude soap. Glycerol (glycerin) is liberated and is either left in or washed out and recovered as a useful byproduct, depending on the process employed. When used for cleaning, soap allows otherwise insoluble particles to become soluble in water and then be rinsed away. For example: oil/fat is insoluble in water, but when a couple drops of dish soap are added to the mixture the oil/fat apparently disappears. The insoluble oil/fat molecules become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-loving) groups on the outside and encasing a lipophilic (fat-loving) pocket, which shielded the oil/fat molecules from the water making it soluble. Anything that is soluble will be washed away with the water. Synthetic detergents operate by similar mechanisms to soap. The type of alkali metal used determines the kind of soap produced. Sodium soaps, prepared from sodium hydroxide, are firm, whereas potassium soaps, derived from potassium hydroxide, are softer or often liquid. Historically, potassium hydroxide was extracted from the ashes of bracken or other plants. Lithium soaps also tend to be hard these are used exclusively in greases. Typical vegetable oils used in soap making are palm oil, coconut oil, olive oil, and laurel oil. Each species offers quite different fatty acid content and, hence, results in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil is sometimes called Castile/Marseille soap, and is reputed for being extra mild. The term "Castile" is also sometimes applied to soaps from a mixture of oils, but a high percentage of olive oil. Fats containing a high percentage of lower and unsaturated fatty acids give soaps that are readily soluble in cold water, that have good foaming properties even in cold solutions and they are not readily salted out. Although Palm oil, which contains high percentage of long chain saturated acids are used in soap production, as general rule, mixtures of different fats are used to impart optimum properties to the soap for every specific use (FAO, 1993). Detergents are produced from long chain alcohols gotten from fats by converting them into salts of alkyl hydrogen sulfates.
Biodiesel production: Biodiesel production is the process of producing the biofuel/biodiesel, through the chemical reactions: transesterification and esterification. This involves vegetable or animal fats and oils being reacted with short-chain alcohols (typically methanol or ethanol).



















CHAPTER THREE
3.0 MATERIALS AND METHODS
3.1 Sample Collection
The vegetable oils (palm oil, groundnut oil, olive oil, castor oil and palm kernel oil) to be analyzed were bought in neat bottles from Swali market, Yenagoa Bayelsa State, Nigeria. The samples were labeled 1-5 and were stored at room temperature in fume cupboard to prevent exposure to light which could also altered the oil properties.
3.2 Apparatus/Instruments Used
Burette (25 ml)
Retort stand and clamp
100 ml measuring cylinders
100 ml beakers
10ml measuring cylinder
100ml volumetric flask
Stoppered bottle (250 ml)
Analytical balance
3.3 Materials
5g of palm oil
5g of groundnut oil
5g of olive oil
5g of castor oil
5g of palm kernel oil
Wij's reagent (ICl 0.2M)
Sodium thiosulphate (Na2S2O3 0.1M)
Potassium Iodide (KI 10g/l)
Starch indictor (1g/l)
Chloroform (10 ml)
3.4 Methods
Iodine value were determined according to the titrimetric method of Pearson (1970). 5g of the vegetable oil sample were weighed into 250 mL conical flask and 10 mL of chloroform were added to dissolve the oil sample, 25 mL of the Wijs reagent (ICl) were added. The flasks were sealed, shaken thoroughly and placed in a fume cupboard for 11 hours. After the 11 hours, 10 mL of 10% potassium iodide (KI) were added to the sample solution. The sample solution were immediately titrated with 0.2M sodium thiosulphate (Na2S2O3). The samples were titrated to a yellow straw colour and then 1 mL of the 1% starch solution were added to the solution which results to a dark-blue colouration of the solution and titration continues until the dark-blue colour disappears leaving behind a clear solution with thorough shaking of the conical flask throughout the titration process in order to ensure that all the iodine were removed from the chloroform layer.
At the same time, a blank solution were set up containing only 25 ml of Wij's reagent and 10ml of chloroform titrated with 0.2M sodium thiosulphate until a clear solution were observed. The titration processes were repeated with the other four oil samples.
The volume of the sodium thiosulphate in the burette were recorded in a data table. One blank of each trial and one test sample of each trial were utilized. The difference between the blank (B) and test (T) reading (B-T), gives the number of ml of 0.2M sodium thiosulphate needed to react with the equivalent volume of iodine.
The iodine value from the above experiment were calculated from the average titre volume of sodium thiosulphate (Na2S2O3) used in the titration of both the sample and the blank and were plugged into the relation (Singh et al., 1981).
Iodine Number = M (B- T) (12.69)
W
Where "M" = Molarity of the standard sodium thiosulphate solution,
Where "T" = the volume of sodium thiosulphate required to titrate the test solution containing the oil samples.
W = the weight in grams of the sample
Where "126.9" is the molecular weight of iodine per 100g of the oil sample










CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
The results of this research work are summarized using tables as shown below:
Table I: Titration values of Groundnut oil
Titration
Blank
1
2
3
Final Burette Reading (ml)
170.00
0.60
0.50
0.60
Initial Burette Reading (ml)
0.00
0.00
0.00
0.00
Titre (ml)
170.00
0.60
0.50
0.60
Average titre = 0.60+0.50+0.603 = 1.703 = 0.57±0.06 ml
Table II: Titration values of Olive oil
Titration
Blank
1
2
3
Final Burette Reading (ml)
170.00
10.40
10.30
10.50
Initial Burette Reading (ml)
0.00
0.00
0.00
0.00
Titre (ml)
170.00
10.40
10.30
10.50
Average titre = 10.40+10.30+10.503 = 31.203 = 10.40±0.10 ml


Table III: Titration values of Palm oil
Titration
Blank
1
2
3
Final Burette Reading (ml)
170.00
63.60
63.80
64.00
Initial Burette Reading (ml)
0.00
0.00
0.00
0.00
Titre (ml)
170.00
63.60
63.80
64.00
Average titre = 63.60+63.80+64.003 = 191.403 = 63.80±0.20 ml
Table IV: Titration values of Palm Kernel oil
Titration
Blank
1
2
3
Final Burette Reading (ml)
170.00
97.10
98.00
97.80
Initial Burette Reading (ml)
0.00
0.00
0.00
0.00
Titre (ml)
170.00
97.10
98.00
97.80
Average titre = 97.10+98.00+97.803 = 292.903 = 97.63±0.47 ml
Table V: Titration values of Coconut oil
Titration
Blank
1
2
3
Final Burette Reading (ml)
170.00
150.30
150.10
150.50
Initial Burette Reading (ml)
0.00
0.00
0.00
0.00
Titre (ml)
170.00
150.30
150.10
150.50
Average titre = 150.30+150.10+150.503 = 450.903 = 150.30±0.20 ml

Table VI: Showing the Iodine Values of Five Different Vegetable Oils
Vegetable oils
Iodine value (g I2/100g)
Food Safety and Standards Authority of India (FSSAI 2011)
Groundnut oil
86.00
85 - 99
Olive oil
81.01
75 - 94
Palm oil
53.91
45 - 56
Palm kernel oil
36.74
10 - 23
Coconut oil
10.00
7.5 - 10


4.2 Discussion
The iodine value equals the number of grams of iodine required to saturate the fatty acids present in 100g of the oil. Oils rich in saturated fatty acids have low iodine values, while oils rich in unsaturated fatty acids have high iodine values (Bennion, 1995).
In the above experiment, iodine is gradually added to a fixed volume of the oil sample dissolved in chloroform. As long as double bonds are available, the colour of iodine does not appear in the solution as the iodine is absorbed by the double bonds. When all the double bonds are saturated, the colour of iodine appears in the solution. Iodine monochloride (Wijs reagent) reacts with the unsaturated bonds to produce a di-halogenated single bond, of which one carbon bond to an atom of iodine.
 


 After the reaction is complete, the amount of iodine that has reacted is determined by adding a solution of potassium iodide (KI) to the reaction product.
ICl + KI KCl + I2
This causes the remaining unreacted ICl to form molecular iodine. The liberated iodine (I2) is then titrated with a standard solution of 0.2 M sodium thiosulphate.
I2 + 2 Na2S2O3 2 NaI + Na2S2O4
Starch is used as the indicator for this reaction so that the liberated iodine will react with starch to give purple coloured product and thus the endpoint can be observed.
The iodine value is an important characteristic of oils as it indicates the proportion of unsaturated fatty acids present.
The iodine values of groundnut oil from the above experiment were found to be 86.00g I2/100g. These values are lower than that obtained by Musa, et al., (2012) with iodine values of 95.87±0.15g I2/100g.
The iodine values of palm oil were found to be 53.91g I2/100g. These values are comparable to that of Amira, et al., (2004) with iodine values ranging from 50.08-58.90g I2/100g. The iodine values of palm oil obtained are lower than that of groundnut oil.
The iodine values of palm kernel oil were found to be 36.74g I2/100g. These values are lower than that obtained by Atasie and Akinhanmi (2009) with iodine values of 41.24g I2 /100g. The iodine values of palm kernel oil obtained are lower than that of groundnut oil and palm oil.
The iodine values of olive oil were found to be 81.01g I2/100g. These values obtained are comparable to that of Ibrahim, et al., (2008) with iodine values ranging from 79.44-91.38g I2/100g. The iodine values of olive oil obtained are higher than that of palm kernel oil and palm oil but lower than that of groundnut oil.
The iodine values of coconut oil were found to be 10g I2/100g. The value obtained was lower than that of Sani, et al., (2014) with iodine value of 46.8±0.63g I2/100g. The iodine values of coconut oil obtained are lower than that of groundnut oil, palm oil, palm kernel and olive oil.
This difference arises principally from the differences in fatty acid composition of these oils (Akinhanmi and Atasie, 2008).
High iodine value justifies utilization of the oil in soap and shampoo productions (Hassan, et al., 2007). Groundnut oil is an example of nondrying oils whose iodine numbers are less than 100 (Kochhar, 2007), they have the advantage of not undergoing oxidation to form a film, hence are useful in the manufacture of soaps (Kochhar, 2007). The coconut oil has a very low iodine value because of the saturated fatty acids present. The blend has a moderately high iodine value which makes it suitable for soap making but does not make a soft soap because of the presence of coconut oil. The higher the number for an oil, the greater the percentage of these acids, and thus the softer the soap produced from the oil. The soft oils have high iodine numbers and are readily oxidized. The iodine value thus indicates the hardness of the soap, the lower the number, the harder the soap produced. The variation in colours is due to the degree of unsaturation of the fatty acids. Increase in double bonds causes increase in intensity of colour.
CHAPTER FIVE
5.0 CONCLUSION AND RECOMMENDATION
5.1 Conclusion
Based on findings and result so far, it is evidently clear that iodine value of oil determines how the oil is defined, its uses and applications. Iodine value is an indicator of the presence of double bonds in the molecular structure of fats and oils, which influences the long term stability properties of the oil (i.e. important for storage). It has been reported that oil with low iodine value improves the stability and good yield of the liquid oil (Tan et al., 2002).
The more iodine is attached, the higher is the iodine value, and the more reactive, less stable, softer, and more susceptible to oxidation and rancidification is the oil.
The iodine values of the five vegetable oil samples analyzed were less than 115, therefore they are considered to be non-drying, and at such they can be used for soap making (hard soaps) and in food products. Non-drying oil is oil which does not harden when it is exposed to air. This is as opposed to a drying oil, which hardens (through polymerization) completely, or semi-drying oil, which partially hardens. Oils with an iodine number of less than 115 are considered non-drying (Ned, et al., 1995). The result of these findings shows that the oils are of good nutritional value and are good for industrial applications; hence the oils pose no significant health risks to consumers Also, the iodine values of the oil samples did not exceed the permissible level prescribed by Food and Safety Standard Authority of India (2011).
5.2 Recommendation
It is therefore recommend that a more efficient extraction processes should be employ in the extraction of these vegetable oils from its source.

REFERENCES
Atasie, V.N and Akinhanmi, T.F. (2009). Extraction, compositional studies and physic-chemical characteristics of palm kernel oil. Pakistan Journal of Nutrition 8(6):800-803.

Amira, P. O., Babalola, O.O., and Oyediran A. M. (2014). Physicochemical properties of palm kernel oil. Current Research Journal of Biological Sciences 6(5): 205-207

Akububugwo, I.E. and Ugbogu, A.E. (2007)."Physicochemical studies on oils from five selected plant seeds". PakistanJ Nutritn.; 6: 75-78.

AOCS, (2007). Sampling and Analysis of Commercial Fats and oils American Oil Chemists Society Official Methods. AOCS Press, Champaign, Illinois, USA.

Alexander, D.D., Cushing, C.A., Lowe, K.A., Sceurman B. and Roberts, M.A. (2009) Meta-analysis of animal fat or animal protein intake and colorectal cancer. American Journal of Clinical Nutrition.

Applewhite, T. H. (1978). Fats and Fatty Oils: Encyclopedia of Chemical Technology, (3rd Edition). New York: John Wiley and Sons Inc.

Barku, V.Y., Nyarko, H.D. and Dordunu P. (2012). Studies on the Physicochemical Characteristics, Microbial Load and Storage Stability of Oil from Indian Almond Nut (Terminalia catappa L.). Food Science and Quality Management. 8: 9-17.

Benoitvical, F., Valentin, A., Mallic, M. and Bassierc, J.M. (2001). Antiplasmodial activity of Colchlospermum planchonii and C. tinctorium tubercle essential oils. J. Essent. Oil Res., 13: 65-67.

Bennion, M. (1995). Introductory Foods, (10th Edition). New Jersey: Prentice-Hall Inc.


Bligh, E.G and Dyer, W.J. (2007)."A rapid method of total lipid extraction and purification". Journal of Biochemical Physiology.37: 911-917.

Crowe, F.L., Key, T.J. and Appleby, P.N. (2008) Dietary fat intake and risk of prostate cancer in the European Prospective Investigation into Cancer and Nutrition. American Journal of Clinical Nutrition.

Dunn, R. O. (2005). Effect of Antioxidants on the Oxidative Stability of Methyl Soyate (Biodiesel). Fuel Proc. Technol. 86: 1071—1085.

Food and Agriculture Organization of the United Nation, 1993.

Freeman, I. P. (2000). "Margarines and Shortenings". Ullmann's Encyclopedia of Industrial Chemistry.

Frega, N., Mozzon, M. and Lercker, G. (1999). Effects of Free Fatty Acids on Oxidative Stability of Vegetable Oil. J. Am. Oil Chemists' Soc. 76 (3): 325-329.

Gertz, C., Klostermann, S. and Kochhar, S. P. (2000). Testing and. Comparing Oxidative Stability of Vegetable Oils and Fats at Frying Temperature. Eur. J. Lipid Sci. Technol. 102(8-9): 543-541.

Hassan, L.G, Osoba, O., Umar, K.J and Inuwa, M. (2007). Physico-chemical Analysis of Cyperusesculentus oil. Yauri Journal of Arts and Science 1(4).

Ibrahim, H. A., Khaddor, M., Boussab, A., Garrouj, A.D. and Souhial, B. (2008). Physical and Chemical Characteristics of Olive Oils from Cooperatives for Olive Growers in the North of Morocco. International Journal of Basic & Applied Sciences, 14(02).

Kambu, K., Di Phenzu, N., Coune, C., Wauter, J.N. and Angenot, L. (1982). Plants Medicine ET Phytotherapie, p. 34. 87(5):1405-13.

Kochhar, S.L. (2007). Economic Botany in the Tropics 2nd edition. Macmillan India Ltd.
Khanahmadi, M. and Janfeshan, K. (2006). Study on Antioxidation Property of Ferulago angulata Plant. Asian J. Plant Sci. 5(3): 521-526.

Lemos, T.L.G., Matos, F.J.A., Alencar, J.W., Crareiro, A.A., Clark, A.M. and Chesnary, J.D. (1990). Antimicrobial activity of essential oils of Brazilian plants: Phytopther. Res., 4: 82-84.

Musa, M. S., Bello, I., Itumoh, J. E., Bello, K., Bello, A. M. and Arzika, A. T. (2012). Physicochemical Properties of Some Commercial Groundnut Oil Products Sold in Sokoto Metropolis, Northwest Nigeria. Journal of Biological Science and Bioconservation 4: 17-24

Mbatchou, V. C., and Kosoono, I. (2012). "Aphrodisiac activity of oils from AnacardiumoccidentaleL. seeds".Phytopharmacology- International Journal of Phytotherapy Bioactivities of Natatural Product 2: 81 -91.

Nkafamiya, I. I., Maina, H. M., Osemeahon, S.A and Modibbo, U. U. (2010). Percentage oil yield and physiochemical properties of different groundnut species (Arachis hypogaea). African
Journal of Food Science. 4 (7), 418 – 421.

Ned, A. P., Sarah, E. C. and Karen, A. (1995). "Mechanisms of free radical oxidation of unsaturated lipids", 30, pp.277-290.

Njoku, O. U., Boniface, J. A. E., Obitte, N. C., Odimegwu, D. C. and Ogbu, H. I. (2010). "Some nutriceutical potential of beniseed oil". International Journal of Applied Research Natural Product, 2(4): 11-19.

Odoemelam, S. A. (2005). Proximate Composition and Selected Physicochemical Properties of th seeds of African Oil Bean (Pentaclethra marcrophylla). Pakistan Journal of Nutrition. 4(6): 382-283.

Oyedeji, F. O. and Oderinde, R. A. (2006). Characterization of Isopropanol Extracted Vegetable Oils. Journal of Applied Science, 6(11): 2510-2513.
Parry, J., Su, L., Luther, M., Zhou, K., Yurawecz, P., Whitaker, P. and Yu, L. (2005). Fatty acid composition and antioxidant properties of cold-pressed marionberry, boysenberry, redraspberry, and blueberry seed oils. Journal of Agriculture and Food Chemistry, 53:566-573.

Passera, L. S. (2008) Oxidation of Lipids. Plant Food and Human Nutrition, 31: 77-83.

Ramakrishna, G., Prasad, N.B.L. and Azeemoddin, G. (2004). Cold processing neem seed, JNTU, Oil Technological Research Institute, Proceedings of the World Neem Conference, Bangalore, India. 24 –28.

Sani, I., Owoade, C., Abdulhamid, A., Isah, M. and Fakai, F. B. (2014). Evaluation of Physicochemical Properties, Phytochemicals and Mineral Composition of Cocosnuciferal. (Coconut) Oil. International Journal of Advanced Research in Chemical Science 1(8) , pp 22-30

Sieri, S., Krogh, V. and Ferrari, P. (2008) Dietary fat and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition. American Journal of Clinical Nutrition 88(5):1304-12.

Sontos, F.A., Rao, V.S.N. and Silveria, E.R. (1998) Investigations on the antinociceptive effect of Psidium guajava leaf essential oil and its major constituents. Phytotherarapy of Research, 12: 24-27.

Tautorus, C. L., and McCurdy, A. R. (2006). Effect of Randomization on Oxidative Stability of Vegetable Oils, at Two Different Temperatures. Journal of American Oil Chemistry Society. 67(8): 525-530.

Toshiyuki, C. (1999). Prediction of Oxidative Stability Based in Various Chemical Properties for Refined Vegetable Oils. Journal of Japan Oil of Chemical Society 48(8):781-786.

Trease, G.E., and Evans, W.C. (2005). Pharmacology. 15thg Edn. Saunders Publishers, London. Pps 42-44, 221-229, 246-249, 303-306, 331-332, 391-393.

Tan, C. P., Cheman, Y. B., Jinap, S., and Yousie, M. S. A. (2002). Effect of microwave heating on the quality characteristics and thermal properties of RBD palm olein. Innovat. Food Science and Emergence Technology 3:157-163.

Ullah, J., Hamayoun, M., Ahmad, T., Ayub, M., and Zarafullah, M. (2003). Effect of Light, Natural and Synthetic Antioxidants on Stability of Edible Oil and Fats. Asian Journal of Plant Science 2(17-24): 1192-1194.

Vardar-unlu, G., Cadan, F., and Sokmen, A. (2003). Deferera, Polissiou, M. Sokmen, M. Donmez, E and tap bektas, Journal of Agriculture in Food Chemistry, pp. 51-63.

Wallstrom, P., Bjartell, A., Gullberg, B., Olsson, H., and Wirfalt, E. (2007) A prospective study on dietary fat and incidence of prostate cancer (Malmo, Sweden). Cancer Causes Control 18(10):1107-21.









APPENDIX
Calculations
Iodine Number = M (B- T) (12.69)
W
Where "M" = Molarity of the standard sodium thiosulphate solution,
Where "T" = the volume of sodium thiosulphate required to titrate the test solution containing the oil samples.
W = the weight in grams of the sample
Where "126.9" is the molecular weight of iodine per 100g of the oil sample

For Groundnut Oil
B = 56.80 ml, T = 14.50 ml, w = 5g, M Na2S2O3 = 0.2M
= (56.80-14.50) × 0.2 × 126.9 × 100(1000)(5) = 107357.45000=21.47
For Olive Oil
B = 56.80 ml, T = 11.51 ml, w = 5g, M Na2S2O3 = 0.2M
= (56.80-11.51) × 0.2 × 126.9 × 100(1000)(5) = 114946.025000=23
For Palm Oil
B = 56.80 ml, T = 33.17 ml, w = 5g, M Na2S2O3 = 0.2M
= (56.80-33.17) × 0.2 × 126.9 × 100(1000)(5) = 59972.945000=11.99
For Palm Kernel Oil
B = 56.80 ml, T = 17.40 ml, w = 5g, M Na2S2O3 = 0.2M
= (56.80-17.40) × 0.2 × 126.9 × 100(1000)(5) = 99997.25000=20
For Coconut Oil
B = 56.80 ml, T = 15.33 ml, w = 5g, M Na2S2O3 = 0.2M
= (56.80-15.33) × 0.2 × 126.9 × 100(1000)(5) = 105250.865000=21.05











APPENDIX II
Wij's reagent (ICl 0.2M)
Sodium thiosulphate (Na2S2O3 0.1M)
Potassium Iodide (KI 10g/l)
Starch indictor (1g/l)
Chloroform (10 ml