Lemongrass Oil Extraction Methods, Process

Lemongrass oil extraction process

Today we learn the process of lemongrass oil extraction and techniques involved in it.

Lemongrass is native aromatic tall sedge which grows in many parts of tropical and sub-tropical South East Asia and Africa. In India, it is cultivated along Maharashtra, Kerala, Karnataka and Tamil Nadu states besides foothills of Arunachal Pradesh and Sikkim. It was introduced in India about a century back and is now commercially cultivated in these mentioned States. What is lemongrass oil good for? Lemongrass has been used to treat digestive problems and high blood pressure, the essential oil has many other potential health benefits. And, it’s becoming popular oil in aromatherapy to help relieve stress, anxiety, and depression.

Lemongrass is a tropical and sub-tropical, grassy plant used in cooking and herbal medicine. Extracted oil from the lemon leaves and stalks of the lemongrass plant, lemongrass essential oil has a powerful, citrus scent. It does often establish in soaps and other personal care products.

Cultivating and harvesting lemongrass oil:

Lemongrass is native to the tropical countries of India, Cambodia, Indonesia, Guatemala, Sri Lanka, and Malaysia. It grows upright in dense bunches and thrives in moist, warm climates with well-drained, loose, dry, loam soils that have a pH level between 4.3 and 8.4. Lemongrass leaves are a green color with sharp edges much like grass that grows on lawns but much larger. It requires full sun and a soil temperature that is between 21°C and 24°C (70°F to 75°F). Lemongrass requires adequate water drainage requirement, as disproportionate watering will lead to lower oil content.

Lemongrass flowers grow in the winter season. The first harvest is normally obtained after 4 to 6 months of transplanting seedlings. Subsequent harvests are done at intervals of 60 to 70 days depending upon the fertility of the soil and other seasonal factors. Under normal conditions, three harvests are possible through the first year, and 3 to 4 in subsequent years, depending on the management practices followed.

Lemongrass can be harvested 6-9 months after the slips are planted and can be harvested as frequently as once every month through the growing season. Cutting stimulates growth and allowing the plant to develop too large will lead to a reduced oil yield. The lemongrass is harvested in the morning on a dry day to allow the evaporation of dew and to avoid loss of the plant’s color due to heat. When harvested mechanically, sharp tools and machinery are used in order to make sure a clean cut and to avoid splitting the edges of the leaves. If the plant is cut too low, the lemongrass leaves will retain less oil, thus the optimal oil quality is in the higher parts of the leaves. Allowing the plants to mature until before the winter months will make sure that the root reserves are fortified and that the foliage will protect the plant against winter frost. After winter, Lemongrass can be used for compost or mulch or it may be harvested and distilled. Ideally, Lemongrass leaves will keep their green color and be free of fungi. In organize to ensure this, Lemongrass leaves must be dried as soon as possible within 24 hours and a conventional dryer may be used for this. An extended drying period, such as in the case of it being left out in the sun to dry, will cause the leaves to lose color and the aroma value to diminish. Once harvested, leaves can be stored in shade for up to 3 days without the oil yield or quality being compromised.

Harvesting is completed with the help of sickles; the lemongrass plants are cut 10 cm above ground-level and allowed to wilt in the field, before transporting to the distillation site. The Lemongrass is then steam or hydro distilled.

Post-harvest management:

Drying: The lemongrass has been allowed to wilt for 24 hours before the distillation as it reduces the moisture content by 30% and improves oil yield. The lemon crop is chopped into small pieces before filling in the stills. It can be distilled in similar distilleries as used for Japanese mint in India.

Plant Samples

Lemongrass (Cymbopogon Citratus) leaves were collected from plants. The lemongrass plant sample was freshly cut, 10cm from the root, in the morning of the day they were collected. Lemongrass, the percentage essential oil yield for the partially dried leaves was established to be higher than that of the fresh leaves. Thus, once collected, the plant material was dried at room temperature for a maximum four days, then kept in a sealed plastic bag at ambient temperature and protected from the light.

Extraction yield increase by decreasing the particle size due to the higher amount of lemongrass oil released as the leave cells are destroyed by milling. In order to develop the collection efficiency, the plant material was soaked in its distilled water for 30min before the extraction performed.  N-hexane was used as analytical grade reagent in this process.

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Lemongrass oil extraction techniques:

How is lemongrass oil extracted?

Lemongrass Essential Oil is derived from the steam distillation of the fresh or partly dried leaves. After distillation, the oil ranges in color from a yellow color to amber color and exudes a fresh, sweet, grassy and citrus-like aroma. Lemongrass oil is collected by distillation unit of the herbage for 1.5 to 2 hrs. The distillate on cooling separates out into a layer of oil, floating over the bulk of water which is composed by decantation. The lemongrass is distilled either fresh or after wilting.

Distillation

Lemongrass oil is obtained through steam distillation. Lemongrass oil has a strong lemon-like odor. The oil is yellowish in color having 75 to 85% citral and a small amount of other minor aroma compounds. The recovery of oil from the grass ranges from 0.5 to 0.8 percent. It takes about four hours for the complete recovery of the oil.

There are two types of distillation

Hydro-distillation: In this process, the herb is packed in a vessel and partly filled with water. The unit vessel is heated by direct fire without an external boiler. This method of distillation is less efficient, but the unit is simple and cheaper.

Steam distillation:  In this process, steam generated in an external boiler is introduced into the chamber. This process, though involves higher initial cost, is more efficient and the quality of the oil obtained is superior. For example, effective running of 500 liters capacity stem distillation unit, herbage from the 20-acre area is required.

Steam Distillation Method

150g of fresh lemongrass sample was placed into one liter round bottom flask containing 250ml of distilled water. The flask was fitted with a rubber stopper attached to the condenser and heated. Water at 0°C flowed counter-currently during the condenser to condense the ensuring steam. When the water level reached 100°C it started boiling ripping off the essential oil from the lemongrass. When the lemongrass got heated up, the lemongrass essential oil that was extracted from the leaf mixed with the water vapor.

Both passed during the condenser and the vapor was condensed into a liquid. With the use of an ice block, cooling was prepared possible and volatilization of the essential oil was avoided. The condensate was openly collected using a 500ml beaker and then poured into a separating funnel. This produced two layers of oil and water. The tap of the separating funnel was opened to let out the water through the oil was immediately collected into a 100ml stoppered bottle. The bottle was closed strongly to prevent vaporization of the essential oil. The lemongrass oil was collected and the volume of oil obtained was weighed.

What are the advantages of steam distillation?

The advantages of steam distillation are as follows;

• The amount of steam & the quality of the steam can be controlled.
• Lower risk of thermal degradation as temperature normally not above 100°C.
• Most generally used process for the extraction of essential oils on a large scale.

Solvent Extraction Method

150g of the dry sample of lemongrass were weighed from the sliced lemongrass sample and placed in a one-liter clean flat bottom flask. After that, 500ml of N-hexane solvent was poured into the flask. The bottom flask and content were allowed to stand for 36 hrs; this was made to extract all the oil content in the lemongrass and for complete extraction. After which the extract was decanted into another one-liter beaker. 200ml of Ethanol was added to extract the essential oil since lemongrass essential oil is soluble in Ethanol. The mixture was then transferred to a 500ml separating funnel and separated by a procedure called liquid separation process. The content of the separating funnel was and allowed to approach to equilibrium, which separated into 2 layers (depending on their different density). The lower Ethanol extract and the upper Hexane layer were collected into 2 separate 250ml beakers and were placed in a water bath at 78oC. This was done to remove the Ethanol leaving the natural essential oil. The yield of lemongrass oil was determined by weighing the extract on an electronic weighing balance. The variation between the final weight of the beaker with extract and the initial weight of the empty beaker gave the weight of essential oil.

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Raw materials required:

The main raw material is lemongrass. And the grass plants grow well in soils not proper for richer production plants. From sandy and rather dry soils yield moderately more oil and oil of higher citral content than plants from very fertile soils.

A lemongrass plantation has a life cycle of 6 – 8 years. The oil yield reaches its maximum around the third year or fourth year and its annual average value range between 15 and 20 kg/ha with three crops per year. The ratio of lemongrass oil to leaves is equal to 0.348%. Therefore, you will need to obtain about 288 kg of lemongrass to produce 1 kg of essential lemongrass oil.

Depending upon soil and climatic conditions, plantation lasts on an average, for three to four years only. The yield of lemongrass oil is less during the first year, but it increases in the second year and reaches a maximum in the third year; after this, the yield declines. On average, 25 tonnes to 30 tonnes of fresh herbage harvest per hectare per annum from four to six cuttings, which yields about 80 kg of oil. Under irrigated conditions from newly bred varieties, a lemongrass oil yield of 100 to 150 kg/ha is obtained. The clean and fresh herb contains on average 0.3% oil and thick stems are removed before distillation as these are devoid of oil. Formulation of oil:

Lemongrass essential oil 10ml extract was measured and placed in a 120ml beaker containing 5ml of Methanol. Fixatives of 5ml quantity were added to the mixture to improve the longevity of the perfume. The resulting solution was shaken and poured into a 50ml bottle.

The yield of essential oil formula that obtained was calculated by:

The yield of the essential oil = amount of essential oil (in grams) obtained / amount of raw materials (in grams) used

Cost of Lemongrass oil distillation unit:

Steam distillation unit cost approximately – Rs 8 Lakh/ Piece

Lemongrass oil price approximately Rs.600/ per kg.

Equipment used in the lemongrass oil extraction process:

List of machinery used in the extraction of lemongrass oil is;

• Evaporator vessel
• Condenser
• Florentine flask
• Steam boiler
• Pump (condensate)
• Pump (cooling water)
• Cooling tower

Purification of oil

The insoluble particles present in the lemongrass oil are removed by a simple filtration process after mixing it with anhydrous sodium sulfate and keeping it overnight or for 4 to 5 hours. In case the color of the lemongrass oil changes due to rusting then it should be cleaned by steam rectification process.

Storage and Packing of Oil

The lemongrass oil can be stored in containers made up of stainless steel or aluminum or galvanized iron, depending upon the quantity of oil to be stored. The oil must be filled up to the brim and the containers should be kept away from direct heat and sunlight in cool or shaded places.

Lemongrass oil benefits:

Some of the benefits of lemongrass oil are mentioned below;

• Aromatic Use: lemongrass oil used as part of your aromatherapy session, it will induce a feeling of positivity and motivation. However, you should know that you can use its scent to repel insects.
• Topical Use: Dilute the lemongrass oil and rub it on your skin before you go outside this may protect you from free radicals. What is more, you can apply topically after a hard workout to muscle relaxation and quicker recovery.
• Lemongrass or lemongrass oil is used as a natural remedy to heal wounds and help prevent infection.
• Muscles and tendons that tighten up can be eased with lemongrass oil. The oil will help develop blood circulation and provide immediate pain relief by soothing muscle spasms. Backaches, muscle knots, pulled muscles, and sprains can be alleviated after rubbing the problem areas with diluted lemongrass oil because of the active anti-inflammatory agents it contains.
• Lemongrass oil helps reduce pain in muscles and joints, pain resulting from viral infections, and soreness caused by exercise.
• Lemongrass oil is a natural antiseptic and astringent. It acts as a skin tone and can help keep hair and nails healthy and glowing. For overall hair and skin care, add a few drops to shampoo and lotion. To relieve an itchy scalp and help decrease hair loss, massage a few diluted drops onto your scalp for a few minutes, leave it on for half an hour, and rinse off. It will leave hair looking shiny and smelling fresh.

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