Plantlet The Blogging Platform of Department of Botany, University of Dhaka
Oil
Oils are liquid at room temperature (18-24 C) and usually contain oleic acid. On the other hand, fats are solid at room temperature and contain stearic or palmitic acid.
Definition
Oils and fats are water insoluble substances called lipid, consisting of a mixture of triglycerides and containing also small amount of glycerol and fatty acids.
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Classification
Oils can be classified into broad classes:
1. Essential oils or volatile oils.
2. Fatty oils or non-volatile oils.
1. Essential oils
- Essential oils evaporate in contact with air and possess a pleasant taste and strong aromatic odour.
- They are very complex chemically.
- They are usually tarpenes. However, several essential oils can also be aldehydes, ketones, alcohol or phenol based compounds.
All directly aromatic plants contain essential oils. They occur in some 60 families but particularly from the members of the families Larvaceae, Myrtaceae, Apiaceae, Lamiaceae, Rutaceae, Oleaceae, Compositeae, Rosaceae etc.
Methods of oil extraction
The essential oils are extracted from the plant tissues by various methods. There are three principal methods:
1. Distillation
2. Expression
3. Extraction by solvents.
- Some essential oil and oil yielding plants:
1. Rose oil or, otto of roses or attar
Species: Rosa damascene.
Family: Rosaceae.
English name: Damask rose.
Part used: Flower.
Plant type: A priekly shrub.
Uses:
2. Orange oil
Species: Citrus sinensis.
Family:
English name: Sweet orange.
Part used: Peels of fruits and flowers.
Uses:
3. Cinnamon oil
Species: Cinnamomum zeylanicum.
Family: Lauraceae.
English name: Cinnamon.
Bengali name: Daruchini.
Part used: Leaves.
Uses:
4. Ylang ylang oil
Species: Cananga odorata.
Family: Annonaceae.
English name: Ylang Ylang tree (flower of flowers).
Part used: Flower.
Uses:
5. Calamus oil
Species: Acorus calamus.
Family: Araceae.
Englsih name: Sweet flag.
Part used: Rhizome.
Uses:
6. Jasmine oil
7. Lemongrass oil
8. Khus oil or oil of vetiver
9. Sandol wood oil
10. Eucalyptus oil
11. Camphor oil
12. Clove oil
13. Champaca oil
14. Mint oil
2. Fatty oils
- Fatty oils or non-volatile oils don’t evaporate or become volatile, and they can’t be distilled without being decomposed.
- These oils are also known as fixed oils.
- Chemically these vegetable fatty oils are also close to animal fats. They consist of glycerine in combination with a fatty acid. Fatty oils are insoluble in water but soluble in various organic compounds.
Classification
They are categorised into 4 groups:
i. Drying oils
ii. Non-drying oils
iii. Semi-drying oils
iv. Fats or tallow
i. Drying oils
These are those types of oils which are able to absorb O2 and exposure dry into thin elastic films. These oils are of great importance in the paint and varnished industries. Some examples are:
1. Linseed oil
2. Soyabean oil
3. Candlenut oil
4. Walnut oil
5. Niger seed oil
6. Safflower oil
7. Poppy oil
8. Hemp oil
ii. Semi-drying oil
They absorb O2 slowly and only in limited amount. They form a soft film only after a long exposure. Some of these oils are edible; others are used as illuminants or in making soaps and candles.
Some examples are:
1. Cotton seed oil
2. Sesame oil
3.
4. Sunflower oil
5. Corn oil
iii. Non-drying oils
It remains liquid at room temperature and don’t form a film. These oils are edible, can be used for soap and lubricants.
Examples include:
1. Olive oil
2. Peanut oil
3. Castor oil
4.
5.
iv. Vegetable fats or tallow
Fats are solid or semi-solid at room temp. They are edible and are also useful in the manufacture of soap and candle. Drying and semi-drying oils are of more frequent occurrence in plants of temperate regions, whereas non-drying and fats are mostly in the plants of tropical regions.
Examples:
1. Coconut oil
2. Palm oil
3. Cocoa butter
4. Carapa fat
5. Mowra fat or mohua butter
6. Nutmeg butter
7. Chinese vegetable tallow
8. Pongan oil
