There are several ways to extract tea polyphenols from tea:
1. Traditional process: using water or ethanol as solvent, heating to 80℃ in water bath and extracting for many times. After mixing the extractive solutions, extract with chloroform of equal volume, separate chloroform phase, extract with ethyl acetate for many times, recover most of ethyl acetate, concentrate to near dryness, freeze-dry, and repeatedly recrystallize with deionized water to obtain refined products. However, the disadvantages of this method are time-consuming and troublesome operation, large solvent consumption, high toxicity, high cost, low extraction rate, high extraction temperature and easy oxidation and deterioration of tea polyphenols.
2. Microwave radiation extraction of tea polyphenols: the extraction solvent is 50% ethanol, the power is 320 watts, the extraction time is 18 seconds, and the liquid-solid ratio (mL/g) is 1: 9. Under these conditions, the extraction rate of tea polyphenols was 92.7%. Compared with traditional Soxhlet extraction, the biggest advantage of microwave extraction is greatly shortened extraction time and high extraction rate. Compared with supercritical carbon dioxide extraction, it has the advantages of low cost, less investment and high extraction efficiency. But not suitable for laboratory operation.
3. According to the references and related materials, the experimental scheme is obtained:
1. experimental principle: tea polyphenols are extracted by using the property that tea polyphenols are soluble in ethanol and ethyl acetate and insoluble in chloroform.
2. Experimental equipment and reagents:
Equipment: 250ml three-necked flask, cloth bag, evaporating dish, separating funnel, etc.
Reagents: tea, sodium carbonate, ethanol, chloroform, ethyl acetate, distilled water, etc.
3. Experimental steps:
A) extraction: add 2g of sodium carbonate into the crushed 10 g tea leaves, put them into a cloth bag, put them into a three-necked flask, add 50ml of ethanol, heat and boil for 0.5h, pour the extract into an evaporating dish, then wash the tea bag with 10ml ethanol, and combine the washing solutions into the extract.
B) Separation and purification: put the evaporating dish containing the extractive solution on an asbestos net, heat and concentrate until the volume of the extractive solution is about 20ml per month, after cooling to room temperature, move the concentrated solution into a separatory funnel, add the same amount of chloroform, and extract twice (the extraction should be lightly vibrated to prevent emulsification), and the water layer is used to prepare tea polyphenols. The water layer extracted with chloroform is extracted twice with the same amount of ethyl acetate for 20min each time, the ethyl acetate extracts are combined, the ethyl acetate is recovered by vacuum distillation in a water bath (or rotary evaporator), the residual liquid is transferred to a clean and dry evaporating dish while it is hot, heated and concentrated to near dryness in a steam bath, cooled to room temperature, then freeze-dried in a refrigerator, and the white powdery crude tea polyphenols and the crude tea polyphenols are recrystallized with distilled water to obtain refined tea polyphenols. After drying, weighing and calculating the yield.
What is the function of tea polyphenols? How to extract?
Traditional methods for preparing tea polyphenols from tea mainly fall into the following three categories.
Soak tea leaves in polar solvent by solvent extraction, then separate the extract by liquid-liquid extraction, and finally concentrate to get the product. At present, this method is mainly used in industrial production. The product yield is 5%~ 10%, and the product purity is 80%~98%. The solvents used are acetone, ether, methanol, hexane and chloroform. This method has high production cost and is easy to cause pollution.
Ion precipitation method is to precipitate tea polyphenols with metals to separate them from caffeine. This method uses heavy metals toxic to human body as precipitant, so the products produced by this method are difficult to meet the requirements of food and pharmaceutical industries.
Column separation preparation methods include gel column method, adsorption column method and ion exchange column method. The key of this technology is column packing and leaching. The results show that the yield of tea polyphenols is between 4% and 8% and the purity can reach 98% by column separation preparation method, but the column packing is very expensive and needs a variety of organic solvents to elute, which is obviously not suitable for industrial production.
There are some problems and shortcomings in the above traditional methods, and the products can not meet the requirements of food additives and pharmaceutical industry in terms of safety, price and purity. In order to solve these problems, recently, through repeated experiments by relevant experts, a new process of preparing high-purity tea polyphenols by combining supercritical CO2 extraction technology with traditional extraction, concentration and extraction technology was successfully developed. This process not only improves the purity and yield of tea polyphenols. It also meets the requirements of industrial production on raw materials, solvent use, production route, production process safety, product color, yield and purity, and is beneficial to the more effective application of tea polyphenols in medicine and food industry.
Second, the application of tea polyphenols
The main uses of tea polyphenols are as follows:
Antioxidant effect of oil Tea polyphenols are antioxidants of natural oils. Its antioxidant activity is better than that of synthetic antioxidants such as butylated hydroxyanisole (BHA) and dibutyl hydroxytoluene (BHT), and it is also better than VE. It can be widely used in food industry to prevent and delay the oxidation or rancidity of oil.
Pigment protection tea polyphenols can prevent natural pigments and β -carotene from degrading and fading, which is said to be 20 times higher than VC.
Deodorant Because tea polyphenols have a good effect on removing the odor of methyl mercaptan, Japan used it to make deodorized chewing gum and cigarette filters, which can remove and prevent the bad breath of smokers.
Antioxidant and anti-aging tea polyphenols can eliminate excessive free radicals in human body and slow down human aging. A large number of experiments show that the antioxidant activity of tea polyphenols is stronger than VE, and the effect is better if it is combined with VC and VE.
Anti-caries tea polyphenols can strongly inhibit cariogenic bacteria, significantly reduce plaque and periodontal index, but have no effect on other beneficial microorganisms in the oral cavity.
The antibacterial effect of antibacterial and antiviral tea polyphenols is that polyphenols can precipitate bacterial proteins and denature and inactivate them. Based on the antibacterial and antiviral principle of tea polyphenols, catechins have been used in air conditioners abroad. Since 1998 went on the market, this new air conditioner has been well received by the market.
Tea polyphenols have the effects of reducing blood lipid and inhibiting atherosclerosis, and play an important role in body fat metabolism, which can obviously inhibit the increase of cholesterol content in plasma and liver and promote the excretion of lipid compounds from feces, so it can not only prevent atherosclerosis, but also lose weight.
Tea polyphenols, especially catechin derivatives, have many pharmacological effects, such as inhibiting the proliferation of cancer cells, anticancer and antimutagenesis. In addition, catechin derivatives can also reduce the toxic effect of heavy metals on human body and have anti-radiation effect. An American company has used this function to develop foundation cream cosmetics. The product label function is to prevent skin cancer caused by ultraviolet radiation and prevent early skin aging.
In other aspects, the application of tea polyphenols in fish oil products can effectively prevent the peroxide decomposition of polyene esters and acids, and its antioxidant capacity is stronger than VE. Tea polyphenols oil-soluble emulsion used in food blending oil can effectively prolong the induction period of rehabilitation, showing stronger antioxidant capacity than powder.
Tea polyphenols have become a new medicine and food additive. At present, in addition to tea polyphenols tablets and capsules, they are also widely used as antioxidants and food additives, and are used in cereals, oils, convenience foods, aquatic products, meat products, condiments, sweets, beverages and other foods. Products are in short supply, and the development and application prospects are very broad. ...
How to extract tea polyphenols from tea?
Extraction method of tea polyphenols:
1, solvent extraction
Solvent extraction is the most traditional extraction process, and more than ten kinds of extraction processes have been developed successively. Tea polyphenols are easily soluble in water, alcohol, ether, ketone, ester, etc. So there are two kinds of solvent extraction methods: water extraction and organic solvent extraction. Water extraction method uses water as solvent and is heated in water bath for several times to extract; Mixing extractive solutions, and extracting with chloroform; After the chloroform phase was separated, it was extracted with ethyl acetate for many times. Combining ethyl acetate phases, and concentrating by distillation under reduced pressure; Drying (vacuum, freezing or spray drying) and recrystallizing with deionized water to obtain the product. The method has the advantages of less organic solvent consumption, simple process, low cost, high product purity and low extraction rate. Organic solvent extraction is a traditional method for extracting tea polyphenols, and it is also the most widely used method. The process is relatively simple. Its principle is to use the solubility difference of different compounds in different solvents in tea to extract and separate. Commonly used solvents are water, methanol, ethanol, acetone and ethyl acetate, which are generally extracted by reflux.
Process flow: tea raw materials → solvent extraction → filtration → organic solvent decolorization and decaffeination → extraction → solvent recovery and drying.
→ Crude tea polyphenols. Leaching, impurity removal and extraction are essential steps, and common impurity removal methods include chloroform impurity removal, activated carbon decoloration, petroleum ether impurity removal or low temperature static impurity removal. The differences between the processes are only extraction conditions, extractant, extraction time, pH value, temperature, times and so on. ), impurity removal conditions, extraction conditions. The advantage of solvent extraction is stability and reliability. The disadvantages are: the extraction rate of tea polyphenols is low (generally 5% ~ 6%), the product purity is low, the product is easy to oxidize, and it contains a lot of impurities (such as plant polysaccharide, tea brown pigment, pigment, caffeine, resin and so on). ). Although using organic solvents can improve the extraction rate (up to 1o% ~ 15%), the extract contains not only tea polyphenols, but also impurities such as tea pigments and caffeine. In order to obtain fine products, it is necessary to repeatedly purify and refine, and the extraction process is complicated and tedious, generally requiring three-stage cross-flow extraction. Requires multiple distillations and long heating time; A large number of organic solvents are needed, some of which are difficult to recover, toxic and flammable, which is not conducive to safe production. To sum up, the improvement of solvent method should mainly aim at simplifying the process, reducing the cost, improving the content of effective components and the extraction rate.
Hubei Institute of Chemistry has developed a new solvent extraction method to extract tea polyphenols. The content of tea polyphenols is more than 95%, and the extraction rate of tea polyphenols is 8%- 1 1%, in which catechin content is more than 70% and caffeine is less than 1%. The product quality reached or exceeded the requirements of tea polyphenols for medical care, and passed the expert appraisal organized by Hubei Science and Technology Department in 2000. The extraction process is as follows: the crushed tea powder is extracted twice with an extractant at a certain temperature, the concentrated extract is added with a specific solvent and a decoloring agent to remove impurities, filtered, the mother liquor is concentrated, caffeine is eluted with a solvent, tea polyphenols are extracted with a solvent after being concentrated again, the solvent is distilled, and the tea polyphenols product is obtained after drying. The extraction process is as follows: tea powder extraction → filtration and concentration → precipitation and impurity removal → filtration and concentration → dealkalization and extraction → desolvation → drying → tea polyphenols.
The innovation of this process is that (1) concentrated extract is treated with a specific solvent, which can effectively remove impurities and overcome the filtration difficulties and emulsification problems in the subsequent elution of caffeine and pigment. (2) The specific solution for effectively removing caffeine was screened out, and the caffeine content in tea polyphenols could be reduced to below 0.5% by elution with this solution, without affecting the extraction rate and content of tea polyphenols.
2. Metal ion precipitation method
The principle of precipitation method is to extract tea polyphenols by using the property that tea polyphenols can be complexed with some substances to form precipitation under certain medium conditions, so that they can be separated from the leaching solution, and then from caffeine, monosaccharides, amino acids and other components in the aqueous solution. The overall process flow is as follows: tea raw material-hot water extraction-filtration-precipitation-solubilization-extraction-concentration-vacuum drying to obtain crude tea polyphenols. It is reported that there are four kinds of precipitants used, namely inorganic salts, alkaloids, protein and polymers. Inorganic salts are the most commonly used, and the other three precipitants are still in the experimental stage because of their high cost. There are three kinds of precipitants commonly used for inorganic salts: ① basic salts of heavy metals, such as Pb(OH)Ac and Cu (0H) AC; (2) Hydroxide, such as Ca(OH)2, is cheap, but strong alkali has corrosive effect; ③ Salt ions such as Ca2+,Zn2+, Mg2+, Ba2+ and Fe3+ are promising precipitants. Can be precipitated under alkaline conditions, precipitated under acidic conditions, ......
What is the extraction rate of tea polyphenols in tea (green tea as column)?
Taking black tea and green tea as raw materials, the effects of extraction temperature, extraction time, solid-liquid ratio and solvent concentration on the extraction of tea polyphenols were investigated, and the extraction rate of tea polyphenols was also studied. Combined with orthogonal test, the optimum technological conditions for extracting tea polyphenols by solvent method were determined. The results showed that the optimum extraction conditions of black tea were as follows: solid-liquid ratio 1︰80, ethanol concentration 60%, extraction temperature 50℃ and extraction time 30 min, at which time the extraction rate of tea polyphenols was 20.35%. The optimum extraction conditions of green tea were as follows: solid-liquid ratio 1︰80, ethanol concentration 50%, extraction temperature 50℃ and extraction time 40 min. The extraction rate of tea polyphenols was 25.44%.
How to extract tea polyphenols from tea?
Pulverize tea leaves, take 65438±00g, add 65438±000ml of 20% ethanol, take a water bath at 70~80℃ for 30 minutes, extract for three times, combine the extractive solutions, add 2gZnCl2 as precipitant, add NaHCO3 to adjust the pH value to 6.4~8.0, stand for 60 minutes, centrifuge or filter, and remove the water layer.
Is there any simple way to extract tea polyphenols from brewed tea?
Extracting tea polyphenols is not a simple matter!
Soak tea leaves in polar solvent by solvent extraction, then separate the extract by liquid-liquid extraction, and finally concentrate to get the product. At present, this method is mainly used in industrial production. The product yield is 5%~ 10%, and the product purity is 80%~98%. The solvents used are acetone, ether, methanol, hexane and chloroform. This method has high production cost and is easy to cause pollution.
Ion precipitation method is to precipitate tea polyphenols with metals to separate them from caffeine. This method uses heavy metals toxic to human body as precipitant, so the products produced by this method are difficult to meet the requirements of food and pharmaceutical industries.
Column separation preparation methods include gel column method, adsorption column method and ion exchange column method. The key of this technology is column packing and leaching. The results show that the yield of tea polyphenols is between 4% and 8% and the purity can reach 98% by column separation preparation method, but the column packing is very expensive and needs a variety of organic solvents to elute, which is obviously not suitable for industrial production.
There are some problems and shortcomings in the above traditional methods, and the products can not meet the requirements of food additives and pharmaceutical industry in terms of safety, price and purity. In order to solve these problems, recently, through repeated experiments by relevant experts, a new process of preparing high-purity tea polyphenols by combining supercritical CO2 extraction technology with traditional extraction, concentration and extraction technology was successfully developed. This process not only improves the purity and yield of tea polyphenols. It also meets the requirements of industrial production on raw materials, solvent use, production route, production process safety, product color, yield and purity, and is beneficial to the more effective application of tea polyphenols in medicine and food industry.
Are the extraction processes of tea polyphenols and theaflavins the same? What extraction methods are used in industry now? 10 point
The principle and thinking are the same. I know the extraction process of tea polyphenols, but I have never been exposed to theaflavins. The extraction technology of tea polyphenols is introduced in detail in my space.