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Extraction Optimising Yield for Solid/Liquid Herbal Extraction

| Editor: Doris Popp

A variety of leaves, stems, roots, seeds and barks are used in herbal extraction processes to produce traditional South East Asian and Chinese medicine, medicinal products, instant tea drinks and a wide variety of active ingredients and colours for use in industries such as food and beverage, pharmaceutical and cosmetics. The fundamental technology used has been around for many years, but SPX brings in-depth understanding and technological innovation to ensure yields are high and the process efficient.

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The SPX design ensures an efficient filtration of the solids material, a self draining design and easy discharge of residues.
The SPX design ensures an efficient filtration of the solids material, a self draining design and easy discharge of residues.
(Picture: SPX)

The method for herbal extraction is very similar to making a cup of tea. Raw material is placed in a percolator and a solvent added (for tea this would be hot water). Parameters that affect the quality of the resulting product include temperature, time in the solvent, and ratio of solvent to active ingredient.

Rather than a cup or pot of tea, however, industrial-scale processes produce a few tonnes of product per hour and solvents used include fluids such as ethanol, acetone or ethyl acetate as well as water. The process temperature depends on the liquid utilised and typically varies from 70 °C to 90 °C, or up to 100 °C when water is being used.

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How to Handle Hazardous Solvents

Some solvents, such as acetone, are hazardous and may have regulations associated with management of their residue. To ensure careful treatment of such substances from a health and environmental standpoint, steam can be applied though the wet cake of exhausted material in the vessel, causing the solvent to evaporate. The vapours created are guided to a condensing system and discharged either for recycling within the system or to be transported to a recycling plant, depending on system requirements.

Equipment Developments

Traditional extractors are cylindrical with ingredients being added at the top. The mixture is then stirred to bring the solvent and raw material in contact. However, this method creates issues in the process with dust being swirled through the extract fluid, impacting the downstream process. Separating the liquid and solids at the end of the process for discharge also becomes more complicated.

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