Arachis Oil

ARACHIS OIL

Synonyms

Groundnut oil; monkeynut oil; peanut oil; katchung oil; earth-nut oil.

Biological Source

Arachis oil is obtained by expression of shelled and skinned seeds of Arachia hypogaea Linn., belonging to family Papilionaceae.

Geographical Source

South America (Brazil) is the original home of ground nut and now found in South and Central America, Peru, Argentina, Nigeria, Australia, India, Gambia, and other reasonably warm regions of all countries.

Characteristics

Groundnut plant is a small, prostrate, diffuse, erect, branched, annual herb, 30–60 cm in height, leaves alternate with adnate stipules and yellow papilionaceous flowers. After fertilization, the pedicel elongates rapidly and enters the ground, where the ovary begins to develop into a pod maturing in about two months. Pods or nuts are cylindrical, hard, reticulated, indehiscent, and inflated, 2.5–5.0 cm long, one to three seeded, with pericarp constricted between the seeds. The seeds are covered by a light or deep reddish brown seeds coat, and consisting of two white fleshy cotyledons rich in oil and proteins.

Fruits are dug out by raking the plants from the soil, seeds are separated by machine and expressed in a hydraulic press at ordinary temperature. The remaining oil of cakes is removed by solvent extraction. The two oil fractions are combined and purified.

Cultivation

Groundnut is predominantly a crop of the tropical and subtropical countries, up to an elevation of 1,160 m. It requires plenty of sunlight, timely and evenly distributed rainfall (50–125 cm) during its growth and a long season for its maturation and harvesting. It also requires a high temperature (21–26°) particularly during the nights to induce early flowering. The plant does not stand frost, long and severe drought and water stagnation. Groundnut seeds are sown from April–May to June–July. It requires light, well-drained, loose, friable soil. No regular manuring is done by the growers, and the plant is benefited from green manuring.

Groundnut is susceptible to infection by several fungi, bacteria, and viruses. Some important diseases in India are tikka leaf spot, collar rot, dry root rot, stem rot, rust, bud necrosis, and yellow mould.

Groundnut oil is a nondrying oil belonging to the oleolinoleic acid group of oils. It is pale-yellow in colour or almost colourless liquid with a nutty odour and bland taste. Clouds are formed in the oil at low room temperature. It has acid value 0.08–6, saponification value 188–195, iodine value 84–102; thiocyanogen value 67–73, and hydroxyl value 2.5–9.5. It is very slowly thickens and becomes rancid on prolonged exposure to air. It is miscible with solvent ether, petroleum ether, chloroform, carbon disulphide, benzene, and very slightly soluble in alcohol.

                        Arachia hypogaea

Chemical Constituents

The important constituents of the glycerides of groundnut oil are the fatty acids palmitic (8.3%), stearic (3.1%), oleic (56%), linoleic (26%), arachidic (24%), eicosenoic, behenic (3.1%), and lignoceric (1.1%) acids. Myristic, hexacosanoic, erucic, caprylic, lauric, and trace amounts of odd carbon fatty acids are also present. The principal glycerides of the oil are triolein (11%), dioleolinolein (21%), saturated oleolinoleins (22%), dilinoleoolein (12%), saturated diolein (15%), and saturated dilinoleoolein (6%).

The yellow colour of the oil is due to the presence of carotenoid pigments, chiefly β-carotene and lutein. The unsaponifiable matter consists of sterols, (campesterol, stigmasterol, β-sitosterol and cholesterol), sterol glycosides β-sitosterol-D-glycoside and others), and triterpenoid alcohols (β-amyrin, cycloartenol and 24-methylene cycloartenol). Tocopherols occur free in groundnut oil. Squalene, an unsaturated hydrocarbon, occurs in extremely small amounts in the unsaponifiable fraction. Two other unsaturated hydrocarbons, hypogene, and arachidene, have also been reported.

The kernels contain fixed oil (40–50%), proteins (26.2%), water (1.8%), carbohydrates (20.6%), ash, and high concentration of thiamine. The chief proteins are arachin and conarchin, both are globulins of different solubility. The vitamin content of groundnut is moderate, the largest being in the episperm.

Uses

Groundnut oil is used as an edible oil, in control of pasture bloat, as a substitute for Olive oil, as a solvent in pharmaceutical aid, in hydrogenated state as shortening, in mayonnaise, in confections; for the manufacture of margarine, soap, points, liniments, plasters, and ointments, as vehicle for intramuscular medication and in the laboratory as heat transfer medium in melting point apparatus.

Marketed Products

It is one of the ingredients of the hair oil known as J.P. Nikhar oil (Jamuna Pharma) and Sage baby oil (Sage Herbals).