Shorea robusta seed oil
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Shorea robusta seed oil is an edible oil extracted from the seeds of Shorea robusta. Shorea robusta is known as the Sal tree in India. Sal is indigenous to India and occurs in two main regions separated by Gangetic plain, namely the northern and central Indian regions. The plant belongs to the Dipterocarpaceae botanical family.
Common name in Indian languages
- Common name: Sal
- Hindi:( साल) Sal, Salwa, Sakhu, Sakher
- Marathi: sal, guggilu, rala, sajara
- Tamil: attam, venkungiliyam, kungiliyam
- Malayalam: karimaruthu, kungiliyam, maramaram
- Kannada: ashvakarna, asina, asu, bile-bhogimara
- Bengali: Sal
- Oriya: sala
- Urdu: Ral, Safed dammar
- Assamese: Sal, Hal
- Sanskrit: agnivallabha, ashvakarna, ashvakarnika
This tree is native to the Indian Subcontinent, ranging south of the Himalaya, from Myanmar in the east to Nepal, India and Bangladesh. The tree is widely distributed in tropical regions of India and covers about 13.3% of the total forest area in the country. Sal (Shorea robusta) tree occurs either gregariously or mixed with other trees in Himalayan foot hills and central Indian belt. In the Himalayan foot hill belt it extends up to Assam valley (including Mefghalaya and Tripura) in the east to foothills of north-west Bengal, Uttar Pradesh, Uttaranchal, kangra region of Himachala Pradesh. The Gangestic plains separate the Himalayan foothill from the central Indian belt.
Shorea robusta is a large, deciduous tree up to 50 m tall, having a trunk circumference up to 5 m; these are exceptional sizes, and under normal conditions S. robusta trees attain a height of about 18–32 m and girths of 1.5–2 m. The trunk is clean, straight and cylindrical, but often bearing epicormic branches. The crown is spreading and spherical. The bark is dark brown and thick, with longitudinal fissures deep in poles, becoming shallow in mature trees, and provides effective protection against fire. The tree develops a long taproot at a very young age. The tree grows at 100–1500 m Altitude. The mean annual temperature required is minimum 22-27 and maximum is 34-47 degrees C. The mean annual required rainfall should be between 1000-3000 (max. 6600) mm. S. robusta flourishes best in deep, well-drained, moist, slightly acid sandy to clayey soils. It does not tolerate water logging. The most favourable soil is a moist sandy loam with good subsoil drainage. The availability of soil moisture is an important factor determining the occurrence of S. robusta.
Leaves: Leaves are simple, shiny, about 10–25 cm long and broadly oval at the base, with the apex tapering into a long point. New leaves are reddish, soon becoming delicate green.
Flowers: Flowers are yellowish-white, arranged in large terminal or axillary racemose panicles.
Fruit: Fruit at full size is about 1.3-1.5 cm long and 1 cm in diameter; it is surrounded by segments of the calyx enlarged into 5 rather unequal wings about 5-7.5 cm long In the Fruit 66.4% is kernel and pod, 33.6% is shell and calyx. Usually the fruits ripen in the month of May.
The seed constitutes 33.6% of shell and contains 14-15% fat. It has calyx and wings. The de-winged seeds contain a thin, brittle seed pod. The whole kernel has 5 segments covering the embryo. Two kilograms of seed gives one kilogram of kernel. The chemical composition of the seeds consists of 10.8% water, 8% protein, 62.7% carbohydrate, 14.8% oil, 1.4% fiber and 2.3% ash.
Seed collection-Extraction of oil
Sal (Shorea robusta) is a major means of survival for a large number of forest dwellers in the Central Indian states of Orissa, Chhattisgarh and Madhya Pradesh. These three states include the largest sal belt of the country with sal forest area covering about 45% of their total forest area. Orissa has the largest sal forest area that covers an area of 38,300 km2, followed by Madhya Pradesh with 27,800 km2 and Chhattisgarh with 24,245 km2. Across these three states about 20-30 million forest dwellers, mostly tribals depend on collection of sal seeds, leaves and resins for their livelihood. Storage of Shorea robusta seeds before processing is very crucial and important.Presence of excess moisture deteriorate the oil quality. Excess moisture in the seed encourages Hydrolysis in the seed fat resulting with high F.F.A oil output. So the moisture content should not be more than 6-8% in stored seeds in any condition.
Sal fat is extracted in three methods, one among the three is traditional system. Traditionally fat is extracted by water rendering. The second widely employed mechanical system is rendering oil extraction by oil expeller and rotary mills in village level. The third method is the solvent extraction method. In solvent extraction method the seed is pressed as flakes first in a flaker mill and thus the seed is exposed to solvent extraction.
Characteristics of Shorea robusta (Sal) oil
The extracted crude sal oil/fat is greenish-brown in colour and has a typical odour. Due to the presence of more saturated fatty acids in the oil, it is solid at room temperature. So because of its solidness it is known as sal (Shorea robusta) fat or sal butter. The oil is used as cooking oil after refining. The oil contains 35-45% stearic acid, an 18-carbon saturated fatty acid, and 40-45% oleic acid, which is a mono unsaturated fatty acid, with 18 carbons like stearic acid. The refined oil is used as substitute for cocoa butter in chocolate manufacturing.
Physical and chemical properties of oil
|Appearance||white color solid|
|slip melting point||32-35 °C|
|Refractive Indexat 40 °C||1.4500-1.4600|
Fatty acid composition of oil
|Palmitic acid (C16:0)||2-8|
|Margaric acid (C17:0)||0-5.0|
|Stearic acid (C18:0)||45-60|
|Arachidic acid (C20:0)||0.5|
|Oleic acid (C18:1)||35-50|
Uses of oil
- Sal oil or butter is used for cooking locally and used for soap up to 30%. Refined modified fat substitutes Cocoa butter and used in confectionery industry to great extent and has export demand. Sal butter is used in the manufacturing of edible ghee (vanaspati), paints and pigments, lubricants, auto oil, etc.
- Apart from being a confectionery item, the sal seed oil nowadays can also be used one of the better option for production of the vegetable oil based diesel or biodiesel and its blend in a diesel engine such as direct injection engines. Biodiesel are vegetable oil methyl esters and can be used as a biodegradable transportation fuel in neat form or in blends with petroleum derived diesel in diesel engines. Biodiesel is similar to the conventional petroleum diesel.
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