A.S. Abitogun and F.B. Borokini
Keywords: Cashew nut, extraction, oil, physicochemical, unsaturated fatty acid.
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.
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).
Table 2: Fatty acid composition of crude cashew Nut (anacardium accidentale) oil.
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.
Akinhanmi, T.F., Atasie, V.N., Akintokun, P.O., (2008), Chemical composition and
Akintayo, E.T., (2004). Characteristics and composition of parkia biaglabba and Jatropha
AOAC, (1990), Official method of analysis of the Association of Official Analytical Chemist
Benerdini, E.,(1973), Oil and fat technology , Rome: Publishing house technologic S.R.L.,Pp
Carson, K.F.( 1991), Fat and oil processing INFORM.
Frankel, E.,(1991), Poison ivy, poison oak, poison sumac and their relative pistachios;
Giwa, N.(1992), Waste oil management and environment. A report by Chairman Raw
Lawson, H.(1995): Food oils and fats New York: Chapman and Hall.
Rosengarten, F (1984) The book of edible nuts (5th edition). New
Salunke, D.K., Chavan,R.N., Adsule and Kadan, S.S., (1992) World oil seeds, chemistry,
Winterhalter, P., Mearse, H., Dekker, E.D., (1990), Fruits and volatile compounds in food and