Industry Trends

Plant extraction, as an important means of obtaining active ingredients from natural plants, has a wide range of applications in the fields of medicine, food, and cosmetics. With the increasing demand for natural products, plant extraction technology is also constantly improving and perfecting. This article will provide a detailed introduction to the entire process of plant extraction, including pre-treatment, extraction systems, separation and concentration systems, purification systems, and drying systems. It will also discuss the technical characteristics and optimization directions of each link to provide references for the industrial production of plant extraction.

I. Overview of Plant Extraction Process

The plant extraction process mainly includes pre-treatment, extraction systems, separation and concentration systems, purification systems, and drying systems. Pre-treatment is the basis of the extraction process. By removing impurities, cleaning, and crushing and sieving, it provides suitable raw materials for subsequent extraction. The extraction system is the core link, which uses different extraction methods, such as solvent extraction, ultrasonic extraction, and supercritical extraction, to separate the active ingredients from plants. The separation and concentration system removes impurities and increases the concentration of active ingredients through filtration and concentration techniques. The purification system further removes impurities and improves the purity of the product. Finally, the drying system dries the extract into powder or solid form for easy storage and use.

II. Pre-treatment

(A) Impurity Removal and Cleaning Unit

Plant raw materials often mix with impurities during the collection process. Impurity removal and cleaning is the first step to ensure the quality of the extract. Soaking is a common cleaning method. By immersing plant raw materials in water, the impact and soaking action of water flow can remove surface impurities. Spraying is another cleaning method, which is suitable for plant raw materials with larger volume or irregular shape. In actual production, the appropriate cleaning method can be selected according to the nature of the plant raw materials and the impurity situation. For example, for root and rhizome plants such as ginseng and astragalus, a combination of soaking and spraying can be used. First, the plants are soaked for a period of time, and then sprayed to achieve better cleaning results.

(B) Crushing Unit

Crushing and sieving is another important link in pre-treatment. After crushing, the plant raw materials can increase their specific surface area and improve extraction efficiency. There are many methods of crushing, such as mechanical crushing and air flow crushing. Mechanical crushing is suitable for most plant raw materials. It uses shearing, compression, and other mechanical actions to crush plants into smaller particles. Air flow crushing uses the strong collision and shearing action generated by high-speed airflow to crush plants into fine powder, which is suitable for extraction processes with high particle size requirements. The crushed plant raw materials need to be screened through a sieve to remove large particles that are not completely crushed and ensure the uniformity of the raw materials. For example, in the extraction of active ingredients from tea leaves, the tea leaves are crushed to a certain particle size and then screened through a sieve to obtain uniformly sized tea powder, which is conducive to subsequent extraction operations.

III. Extraction System

(A) Extraction Unit

Extraction is the core link of the plant extraction process. Different extraction methods are suitable for different plant raw materials and active ingredients. Solvent extraction is one of the most commonly used methods. It uses solvents such as water and ethanol to dissolve the active ingredients from plants. The choice of heating method in the solvent extraction process has an important impact on the extraction effect. Steam heating is a traditional heating method with the advantages of high thermal efficiency and uniform temperature, suitable for large-scale production. Electric heating has the advantages of convenient operation and precise temperature control, suitable for laboratory and small-scale production. For example, in the extraction of chlorogenic acid from honeysuckle, water is used as the extraction medium, and steam heating can effectively extract chlorogenic acid.

Ultrasonic extraction is an emerging extraction technology. It uses the cavitation effect of ultrasonic waves to generate local high temperature and high pressure, accelerating the contact and dissolution process between the solvent and plant raw materials. Ultrasonic extraction has the advantages of low temperature, short time, and high extraction efficiency, and is suitable for the extraction of heat-sensitive components. The ultrasonic generator unit shares with the extraction tank, which can achieve uniform distribution of ultrasonic waves. For example, in the extraction of proanthocyanidins from grape seeds, ultrasonic extraction technology is used, and the extraction time is only 1/3 of that of traditional solvent extraction, with an extraction rate increased by more than 20%.

Supercritical extraction is an advanced extraction technology. It uses the solubility of supercritical fluids (such as carbon dioxide) in the supercritical state to extract active ingredients from plants. Supercritical extraction has the advantages of low temperature, no solvent residue, and good extraction effect, but it is costly and relatively inefficient. For example, in the extraction of capsaicin from chili peppers, supercritical carbon dioxide extraction technology is used, and the purity of the extracted capsaicin can reach more than 99%, with no solvent residue.

(B) Optimization of Extraction Technology

In actual production, the appropriate extraction technology can be selected according to the nature of the plant raw materials and the characteristics of the active ingredients, and the extraction process can be optimized. For example, in the extraction of glycyrrhizic acid from licorice, the effects of solvent extraction, ultrasonic extraction, and supercritical extraction were compared. It was found that ultrasonic extraction has a better balance between extraction rate and extraction time. Therefore, ultrasonic extraction technology was selected, and the extraction conditions such as ultrasonic power, extraction time, and solvent dosage were optimized. Finally, the optimal extraction process parameters were determined to improve the extraction rate and product quality of glycyrrhizic acid.

IV. Separation and Concentration System

(A) Separation System (Filtration)

The main function of the separation system is to remove solid impurities and suspended particles from the extract, improving the clarity of the extract. Natural filtration uses gravity to filter the extract through filter materials, but the filtration speed is slow and is suitable for small-scale production. Plate and frame filtration is an efficient filtration method. Through the plate and frame filter press, the extract is filtered through filter materials under pressure, with the advantages of high filtration efficiency and good effect, but filter materials need to be replaced halfway. Centrifugal filtration uses the action of centrifugal force to separate solid impurities from the extract, with the advantages of continuous filtration and high efficiency. Membrane filtration is an advanced filtration technology. It uses the selective permeability of semi-permeable membranes to separate different components in the extract, with the advantages of good filtration effect, high precision, and reusability, but the equipment cost is high. For example, in the extraction of isoflavones from soybeans, membrane filtration technology can effectively remove proteins, polysaccharides, and other impurities from the extract, improving the purity of isoflavones.

(B) Concentration System

The role of the concentration system is to concentrate the active ingredients in the extract, increasing their concentration for subsequent purification and drying operations. Evaporation concentration is one of the commonly used concentration methods. It uses heating to evaporate the solvent in the extract to achieve the purpose of concentration. Single-effect evaporation concentration equipment is simple, but the energy consumption is high. Multi-effect evaporation concentration uses multiple evaporations to improve the utilization rate of thermal energy and reduce energy consumption. Falling film concentration is a special evaporation concentration method. It uses gravity to form a film of the extract inside the heating tube, accelerating the evaporation of the solvent, with the advantages of fast evaporation speed and high concentration efficiency. Membrane concentration uses the selective permeability of semi-permeable membranes to pass the solvent through the membrane through pressure difference or concentration difference, while retaining the active ingredients, thus achieving the purpose of concentration. For example, in the extraction of mogrosides from monk fruit, falling film concentration technology is used to concentrate the extract to a certain concentration, and then subsequent purification operations are carried out to improve the yield and quality of mogrosides.

V. Purification System

(A) Decolorization Process

Decolorization process is an important link in the purification system. It removes pigments and other impurities from the extract to improve the appearance and quality of the product. Common decolorization materials include activated carbon, diatomite, silica gel, alumina, etc. Activated carbon has the advantages of strong adsorption capacity and low price, and is suitable for decolorization of various plant extracts. Diatomite has the advantages of high porosity and good adsorption performance, and is suitable for decolorization processes with high adsorption selectivity requirements. Silica gel and alumina have the advantages of good chemical stability and strong adsorption selectivity, and are suitable for decolorization of specific components. Adsorption is a method of removing impurities through the physical adsorption action between the adsorbent and the impurities. Ion exchange uses ion exchange resins to exchange with impurity ions to achieve decolorization. For example, in the extraction of curcumin from turmeric, activated carbon is used for decolorization treatment, which can effectively remove the pigment impurities in curcumin and make the product color purer.

(B) Alcohol Precipitation Process

Alcohol precipitation process is a commonly used purification method. It separates the active ingredients from impurities by changing the polarity of the solvent. Common alcohol precipitation processes include alkali extraction and acid precipitation, acid extraction and alkali precipitation and alcohol precipitation. Alkali extraction and acid precipitation first use alkaline solvents to extract the active ingredients from plants, and then add acidic solvents to precipitate the active ingredients. Acid extraction and alkali precipitation first use acidic solvents to extract, and then add alkaline solvents to precipitate. Alcohol precipitation uses organic solvents such as ethanol to precipitate the active ingredients. For example, in the extraction of baicalin from Scutellaria baicalensis, the alcohol precipitation process is used. By adjusting the ethanol concentration, baicalin is precipitated, and some impurities are removed, improving the purity of baicalin.

(C) Column Chromatography

Column chromatography is an efficient separation and purification technology. It separates and purifies the extract by passing it through a chromatography column packed with specific packing materials, using the difference in adsorption action between the packing materials and the active ingredients and impurities. Industrial macroporous resins are commonly used column chromatography packing materials, with the advantages of large pore size, strong adsorption capacity, and fast flow rate, suitable for large-scale production. Industrial ion exchange resins have the advantages of strong ion exchange capacity and good selectivity, suitable for the separation and purification of ionic components. For example, in the extraction of stevioside from Stevia rebaudiana, industrial macroporous resin column chromatography technology is used. By optimizing the elution conditions, stevioside can be effectively separated from other impurities, improving the purity of stevioside.

VI. Drying System

(A) Conventional Drying (Air Drying)

Conventional drying removes moisture from the extract by atmospheric high-temperature evaporation to obtain powder or solid. This method is simple to operate, but it is inefficient, energy-consuming, and high temperatures may lead to the loss of heat-sensitive components. For example, in the extraction of essential oil from roses, conventional drying may destroy the volatile components in the essential oil, affecting product quality.

(B) Spray Drying

Spray drying is an efficient drying technology. It atomizes the extract into tiny droplets and dries them into powder rapidly under the action of hot air. Spray drying has the advantages of fast drying speed, good powder shape, and high efficiency, and is suitable for large-scale production. However, the temperature of spray drying is high (100-300℃), which may have a certain impact on heat-sensitive components. For example, in the extraction of catechins from green tea, spray drying technology can dry the extract into powder in a short time, but the drying temperature needs to be controlled to avoid the oxidation loss of catechins.

(C) Freeze Drying

Freeze drying is an advanced drying technology. It pre-freezes the extract at low temperature and then sublimates the ice directly under vacuum conditions to achieve drying. Freeze drying has the advantage of extremely low working temperature (below 0℃), which can maximize the retention of the activity and stability of the active components. However, freeze drying equipment is costly, energy-consuming, and has low drying efficiency, suitable for the drying of high-value-added products. For example, in the extraction of polysaccharides from Ganoderma lucidum, freeze drying technology can effectively protect the biological activity of polysaccharides and improve product quality.

Plant extraction technology has a wide range of application prospects in the fields of medicine, food, and cosmetics. With the continuous progress of technology, the plant extraction process is also constantly optimized and improved. Every link from pre-treatment to drying system has an important impact on the quality and yield of the extract. Through continuous technological innovation and process optimization, the plant extraction industry will take bigger steps on the path of sustainable development and make greater contributions to human health and economic development.