Which components in tea can be effectively extracted by supercritical CO2 extraction?
Tea is a globally popular beverage that contains a variety of active substances, of which tea polyphenols and caffeine are the two most prominent. Tea polyphenols have physiological effects such as antioxidant and anticancer properties, while caffeine, although relieving fatigue and refreshing the mind, excessive intake may lead to sleep disorders and elevated blood pressure. Therefore, decaffeination technology has been emphasized.
China is a major tea producer and exporter, with a large production of green tea, but the storage time is short, and it needs to be further processed as soon as possible. Decaffeination methods include supercritical fluid extraction, water extraction, pressurized extraction with ethyl lactate, resin adsorption, activated carbon adsorption, montmorillonite adsorption, microbial degradation and enzymatic degradation.
Supercritical fluid extraction method extracts caffeine selectively by supercritical carbon dioxide. Water extraction method utilizes the solubility of caffeine in hot water to remove caffeine, but it may lead to the loss of other components in tea. Resin adsorption method and activated carbon adsorption method can separate caffeine, but may lead to loss of tea polyphenols and change of tea broth color. Montmorillonite adsorption method can effectively remove caffeine without affecting other components, but it is less applied. Biodegradation method, including microbial degradation and enzyme degradation, can reduce caffeine content through biological pathway, but the efficiency is low and needs further research.
The application of supercritical CO2 extraction technology in tea processing has made remarkable progress, which can effectively extract a variety of components in tea, including the following aspects:
1. Caffeine removal
Supercritical CO2 extraction technology can efficiently remove caffeine from tea. Through our experience we use supercritical CO2 extraction machine treatment under specific conditions, the caffeine content in tea can be significantly reduced, and the removal rate can reach more than 70%. The optimal process conditions were extraction temperature of 60°C, extraction pressure of 28 MPa, extraction time of 3.5 hours, and water addition of 20%. This method is suitable for dry tea, but not for aqueous system of tea extract .
2. Tea polyphenol extraction
Tea polyphenols are important physiologically active components of tea. Although the solubility of tea polyphenols in supercritical CO2 extraction machine is low, its solubility and extraction rate can be improved by adding entraining agent such as ethanol aqueous solution.
3. Aroma Extraction
The aroma components of tea are complex and unstable, supercritical CO2 extraction machine is especially suitable for extracting various aroma components in tea due to its advantage of low-temperature operation.
4. Tea color extraction
supercritical CO2 extraction machine has also been used to extract pigments from tea. Compared with the conventional organic solvent method, this method can obtain a crude mixture of pigments, but the solvent consumption is high, inefficient and costly. The yield of green pigment can be significantly improved by selecting a suitable entraining agent .
5 Other applications
Supercritical CO2 extraction technology has also been applied to the extraction of essential oils from tea flowers, the extraction and refining of tea seed oil, etc. .
In summary, the progress of supercritical CO2 extraction technology in tea processing shows that this technology has the characteristics of high efficiency, strong selectivity, environmentally friendly, etc. It is suitable for the extraction of a variety of active ingredients in tea, and is of great significance for the deep processing of tea and the improvement of the added value of tea products.