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JOURNAL OF RESEARCH IN NATIONAL DEVELOPMENT VOLUME 7 NO 2, DECEMBER, 2009

PHYSICOCHEMICAL PARAMETERS AND FATTY ACID COMPOSITION OF CASHEW NUT (Anacardium occidentale)  OIL.

A.S. Abitogun and F.B. Borokini
Department of Science Technology, Rufus Giwa Polytechnic, Owo, Ondo State, Nigeria
E-mail:adeboabitogun@yahoo.com

 

Abstract
The crude oil of cashew nut (anacardium accidentale) was extracted by solvent extraction process. The crude oil was assessed for physicochemical parameters and fatty acid composition. The assessment gave the following results, specific gravity (0.97), refractive index (1.47), colour (30.00 units), moisture content (0.00%), flash point (289.000C), fire point (350.000C), smoke point (149.000C), turbidity (125.50jtu) and the yield (52.40%). Others were, free fatty acid (4.52%oleic acid), acid value (7.04%oleic acid), saponification value (145.00mgKOH/goil), peroxide value (7.73meq.peroxide/kg) and iodine value (37.30mg iodine/100g). The fatty acid detected and there values were myristic acid (0.10%), palmitic acid (13.77%) ,palmitoleic acid (0.68%), stearic acid (1.34%), oleic acd (47.79%), linoleic acid (29.67%), linolenic acid (0.01%), arachidic acid (4.07%), behenic acid (2.08%) and lingnoceric acid (0.31%). The percentage yield of 52.40% makes the nut a good source of oil. The total saturated fatty acid of 21.60% and the total unsaturated fatty acid of 78.14% is an indication that the oil may not likely makes congeal at ordinary temperature. The results show that the oil can be refined to edible vegetable oil.

Keywords: Cashew nut, extraction, oil, physicochemical, unsaturated fatty acid.


Introduction
The increasing demand for vegetable oil in recent times is partly due to the nutritional need of teaming population and increasing number industries that require oils and fats as their primary raw materials. In Nigeria, the demand for vegetable oil has ever been widening as industrialist rely mostly on the popular vegetable oil such as palm kernel oil, groundnut oil, soybean oil, cotton seed oil, and coconut seed oil for preparation of various products (Akintayo, 2004). Lipids are important nutritional component in grains and seeds of many fruits. They make soluble vitamins A,B,E and K, which are necessary for the maintenance of health and sources of essential fatty acid, thus contributing to the several metabolic functions (Lawson,1995). Nigeria however, being a tropical country has  wide variations in climatic condition and therefore has a wide variety of wild plants that produce oil. Lack of information on the nutritional composition of many and varied oil seeds indigenous to Nigeria limited the utilization of this seed (Akintayo, 2004).

The cashew tree (Anacardium occidentale) is native to Brazil and lower Amazons. This cashew has been introduced and is a valuable cash crop in the Americas, the West Indies, Madagascar, India and Malaysia (Frankel,1991). Cashew tree will tolerate a wide range of conditions including drought and poor soil, but cannot withstand cold frost. The major producing countries of cashew are Tanzania, India, Mozambique, Srilanka, Kenya, Madagascar, Thailand, Malaysia, Indonesia, Nigeria, Senegal, Malawi and Angola. World Bank data estimate that 97% of production is from wild trees and only 3% is from established plantation (Rosengarten,1984). Cashew is a highly valued edible nut, and yields two ‘oils’- one of these, found between the seed coat (or pericarp) and the nuts, is called the cashew nut shell liquid. It is not a triglyceride and contains a high proportion of phenolic compound. It is used in the industries as a raw material for brake lining compounds, water proofing agent, preservatives, manufacturing of paints and plastics. However, the oil is toxic and corrosive to the skin.

The other oil, which is the edible oil, can be extracted from the nuts, it contains triglyceride but no evidence of commercial processing has been found. Cashew apples are sometimes made locally into fruit juices, wine and pickles. The apples are very sour and stringent until fully ripe, and become edible. A number of processes have now been developed for converting the cashew apple into various products such as formulated juice, jam, syrup, chutney and beverages

(Winterhalter et al,1991). Cashew nut oil is completely neutral when is unprocessed and is the best for human health. It is especially rich in unsaturated fatty acids and is least damaging to heart and arteries. In fact, it constitutes about 47% of the total weight of the nut. Nut often produces oil half their weight, the oil is referred to as ‘good fat’ and the ratio of saturated to monounsaturated to polyunsaturated fatty acid is 1:2:1 which is ideal for human consumption. According to Achal (2005) the relative abundance of monounsaturated fatty acids in cashew nut oil is conducive to promotion of good health and poses no nutritional risk.        

There are studies on the nutritional composition of the seed and the physicochemical properties of the shell nut liquid but little information has so far been provided on properties of the oil. This paper is aimed at a presentation on extracting and assessing the physicochemical parameters and fatty acid composition of crude cashew nut oil.
 
Materials and methods
Cashew samples were obtained from a farm in Uso, Ondo State, Nigeria. These were cracked with manual cashew kernel cutter to separate from the shells. The nuts were dried at 400C in an oven for 5 hours. The covering testa were removed by squeezing and then winnowed to certain cream coloured nuts, dried clean nuts were milled to flour. A soxhlet extractor was used for solvent extraction of the oil and normal

 

hexane as solvent. The crude cashew nut oil samples obtained were assessed for physicochemical parameters and fatty acid composition. The moisture contents, specific gravity, were determined according to official standard method AOAC, (1990).

The refractive index was determined by Abbe Refractometer while colour was determined using Lovibond Tintometer in one inch cell. The colour which was in units was calculated based on (5R+Y-B) where R is red pigment, Y is yellow pigment and B is blue pigment (Carson,1991). The smoke, flash, fire points were measured by American Society of Testing Materials ASTM, (1985). Turbidity was determined using Palm Test Turbidity Tube (ASTM,1985). The chemical properties of the oil sample such as free fatty acid, acid value, saponification value, peroxide value, and iodine value were determined by standard method AOAC, (1990). Analytical test method for fatty acid methylesters was carried out using Agilant 6890 series Gas chromatography filled with enhanced integrator. Nitrogen gas was used as carrier gas, the column initial temperature was 2300C rising at 100Cper minute to a final temperature of 2750C while the injection and detector were maintained at 2300C and 2750C respectively. A polar capillary column of 30 meters in length and 0.32 millimeters diameter was used to separate the esters. The peaks were identified by compares with standard fatty acid methyesters ASTM, (1985).


Results
Table 1: Physicochemical parameters of crude cashew nut (anacardium accidentale) oil samples 


Parameters

Results

Specific gravity

0.97

Refractive index

1.47

Colour (units)

30.00

Moisture content (%)

0.00

Flash point (0C)

289.00

Fire point (0C)

350.00

Smoke point (0C)

149.00

Turbidity (jtu)

125.50

Free fatty acid (% oleic acid)

4.52

Acid value (% oleic acid)

9.04

Saponification value (mg KoH/g oil)

 145.00

Peroxide value (meq peroxide / kg)

7.73

Iodine value (mg iodine/ 100g)

37.30

Yield (%)

52.40

Table 2: Fatty acid composition of crude cashew Nut (anacardium accidentale) oil.


Fatty acid
methyl ester

Fatty
acids

Carbon
number

Results (%)

Methy myristate

Myristic

14:0

0.10

Methyl palmitate

Palmitic

16:0

13.77

Methyl palmitoleate

Palmitoleic

16:1

0.68

Methyl stearate

Stearic

18:0

1.34

Methyl oleate

Oleic

18:1

47.79

Methyl linoleate

Iinoleic

18:2

29.67

Methyl linolineate

Iinolenic

18:3

0.01

Methyl arachideate

Arachidic

20:0

4.07

Behenic acid methyl ester

Behenic

22:0

1.08

Lingnoceric acid methyl ester

Lignoceric

24:0

0.31


Discussion
Table 1 gives the physicochemical properties of cashew nut oil. The yield was 52.40%, this yield was higher than 49.1% reported by Akinhanmi et al, (2008). This might be as result of environmental fat factors. The moisture content was while the colour of the crude oil was 30.00 lovibond units. The high colour value was as a result of high content of red pigment in the oil. However, the value could be reduced during further processing such as bleaching. It  has a specific gravity of 0.97 which showed that it is less  dense than water and a refractive  index of  1.47 was an indication that the oil is not thick as most drying oil. The result of the flash point, fire point and smoke point were 2890C, 3500C and 1490C respectively. These values showed that the oil has a combustion characteristic (Giwa,1992). These values compared favorably with the values reported for crude soybean oil by Salunkhe et al, (1992).
 

These characteristics that are necessary for the confirmation of identity and edibility of oil were free fatty acid and acid alne (Benerdini,1973). The value obtained for free fatty acid and acid value were 4.52 (% oleic acid) and 9.04% oleic acid respectively. These values were indication that the oil can be refined to edible vegetable oil, and apart from this, it implies that the oil may stimulate oxidative deterioration which can result to formation of off–flavour component. However, the acid value was close to 9.04% oleic acid reported by Akinhanmi et al,(2008). The result of the peroxide value was 7.73 meq peroxide/kg. The peroxide value is again an indication that the oil would be susceptible to oxidative rancidity. The saponification value was 145.0 mg K0H/g oil, which is lower than the values for some common edible vegetable oils such as palm oil (196-205 mg K0H/g) and soy beans oil (190-210 mg K0H/g oil) reported by Salunkhe et al,(1992). However, the saporification value was within the same range of some edible vegetable oils as reported by Eromosele et al, (1994).  The iodine value was 37.35 mg iodine/100g.The unsaturated glyceride of oil is the ability to absorb a definite amount of iodine (Benerdini, 1973). This gave an insight to presume that the oil contain high unsaturated hydrocarbon and it will not be stable at ordinary temperature.

Table 2 depict the fatty acid composition of crude cashew nut oil. The fatty acid detected were myristic acid 0.16%, palmitic acid 13.77%, palmitoleic acid 0.68%, stearic acid 1.34%, oleic acid 47.79%, linoleic acid 29.67%, linolenic acid 0.01%, Arachidic acid 4.07%,behenic acid 2.27%, and lignoceric acid 0.31%.Also detected were caprylic acid, cupric acid, lauric acid, and erucic acid but the values were infinitesimal. The fatty acid detected in this sample could be compared with the fatty acid detected in other edible vegetable oils as reported by Guy, (2000). The summary of the fatty acids in the oil were as follows; total saturated fatty acids was 21.60%, while the total unsaturated fatty acid was 78.14%, 0.26% were the percentage of fatty acid undetected. This might be as a result of impurities present in the crude oil. Oleic acid dominates the fatty acid present in the oil. Since unsaturated fatty acids have the highest

percentage, it implies that the oil may not congeal at ordinary temperature.

Conclusion
The results of the investigation carried out on crude cashew nut oil suggest that, if the oil is refined and consumed, it will supply the essential fatty acid needed in the body as this will reduce the risk of cardiovascular diseases in human being. The yield makes it a good source of oil seed and this should encourage the commercialization of the seed as raw material for vegetable oil industries in Nigeria. The result of the physicochemical properties supported the suitability of the oil for consumption as edible vegetable oil rather than industrial application of soap making.
References
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Akinhanmi, T.F., Atasie, V.N., Akintokun, P.O., (2008), Chemical composition and
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Akintayo, E.T., (2004). Characteristics and composition of parkia biaglabba and Jatropha               
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