Tea polyphenol

Tea polyphenols molecules contain multiple active hydroxyl groups (-OH) that can terminate free radical chain reactions in the human body and remove superoxide ions, similar to the effect of SOD. The elimination rate of tea polyphenols for superoxide anions and hydrogen peroxide free radicals is over 98%, showing a significant dose-effect relationship, and its effect is better than vitamins E and C; tea polyphenols have a protective effect on cell membranes and cell walls, and have a very obvious effect on the elimination of lipid peroxide free radicals.

Physical and chemical properties
Tea polyphenols are light yellow to brown aqueous solutions, powdered solids or crystals with a slight tea aroma, astringent taste, easily soluble in water, ethanol, ethyl acetate, and slightly soluble in oils. It has good heat resistance and acid resistance, and is very stable in the range of pH=2~7. It is slightly hygroscopic, and the pH of the aqueous solution is 3~4. It is easy to oxidize browning under alkaline conditions. Catechins account for about 60%~80% of the total tea polyphenols. Among the polyphenols extracted from green tea and its by-products, the content of tea polyphenols is greater than 95%, including catechins 70% to 80%; flavonoids 4% to 10%; gallic acid 0.3% to 0.5%; amino acids 0.2% to 0.5%; total sugar 0.5% to 1.0%. Chlorophyll is mainly pheophytin, with a content of 0.01% to 0.05%.

Main effects
Tea polyphenols refer to the complex of catechins (flavanols), flavonoids and flavonols, anthocyanidins, phenolic acid and phenolic acid polyphenol compounds in tea. Except for phenolic acid and phenolic acid, their structures all have a C6-C3-C6 basic carbon frame with 2-phenylbenzodihydropyran (flavan) as the main body. Among them, catechin compounds are the main components of tea polyphenols, accounting for about 50% to 70% of the total amount of tea polyphenols and 12% to 24% of the dry weight of tea leaves. It is a class of compounds with relatively complex structures, including catechins, gallocatechin, gallocatechin gallate, catechin gallate, etc. The content of tea polyphenols in tea is generally higher in green tea than in black tea, and higher in summer and autumn tea than in spring tea. The main pharmacological effects of tea polyphenols are:
(1) Lowering blood lipids and inhibiting atherosclerosis. Many studies have shown that drinking tea can reduce the cholesterol content in the blood and has obvious anti-atherosclerosis function. This is because tea polyphenols play an important role in the body's fat metabolism, inhibit the increase in cholesterol content in plasma and liver, and promote the excretion of lipid compounds from feces. Therefore, it can not only prevent and treat atherosclerosis, but also has the effect of weight loss.
(2) Strengthen capillaries and lower blood sugar. Tea polyphenols can not only prevent the increase in microvascular permeability caused by excessive fat, but also work together with tea alkaloids to relax the blood vessel wall and increase the effective diameter, which is beneficial to the dilation of human blood vessels, enhance the toughness of microvascular walls, and prevent blood vessel rupture. Experiments have shown that catechins can also effectively lower blood sugar and reduce the risk of diabetes.
(3) Anti-radiation. The earliest report on tea's anti-radiation effect was from Japan. They found that among the survivors of the atomic bomb explosion, those who drank tea regularly had milder radiation sickness. A series of animal experiments showed that tea polyphenols have obvious anti-radiation effects. It is generally believed that the anti-radiation effect of tea polyphenols is related to the fact that tea polyphenols participate in the redox reaction in the body, protect the blood phase, repair physiological functions, and inhibit internal bleeding. In addition, tea polyphenols can reduce DNA damage caused by radiation.
(4) Anti-aging. Lipid peroxidation in the human body is one of the mechanisms of human aging, and free radicals are the main factor of peroxidation in organisms. Tea polyphenols have a strong free radical scavenging effect, which can play an antioxidant and anti-aging effect. Animal experiments have shown that tea polyphenols can inhibit the activity of lipoxygenase and lipid peroxidation in skin mitochondria.
(5) Anti-cancer and anti-mutation. Free radicals may play a certain role in the process of carcinogenesis, so the free radical scavenging effect of tea polyphenols can play an anti-cancer role. Green tea and oolong tea have a significant ability to block the synthesis of nitrosamines.
Application areas
Tea polyphenols are widely used:

(1) It can be added to animal fats such as lard, chicken oil, fish oil, cream, butter, mayonnaise, and vegetable fats such as soybean oil, peanut oil, rapeseed oil, tea oil, corn oil, and palm oil to prevent fat rancidity. The addition amount is 0.005% to 0.05% of the fat content, and the effect is very significant.
(2) Tea polyphenols can be added to fried potato chips, fried instant noodles, fried peanuts, fried fish and other foods at 0.01% to 0.02% of the fat content, which has a significant antioxidant effect and can prevent the fishy smell during the frying process.
(3) In the processing of aquatic products, adding tea polyphenols at a dosage of 0.01% to 0.02% can have significant antioxidant, anti-corruption and deodorizing effects.
(4) Soak various meat products in a solution prepared with tea polyphenols and other additives, with a tea polyphenol concentration of 0.05% to 0.2%, a soaking time of 5 to 10 minutes, and a solution temperature of 60 to 70°C. At this time, the protein on the surface of the meat product and the tea polyphenols will form an airtight hard film. It can make meat products have an antioxidant effect, inhibit bacterial growth and prevent corruption and deterioration. In the processing of preserved foods such as ham, sausage, and bacon, adding 0.01% to 0.02% tea polyphenols can not only inhibit oxidation and corruption, but also reduce the content of nitrite in preserved foods, giving preserved foods a delicious aroma.
(5) Adding tea polyphenols to dairy products can not only eliminate odors, but also prevent oxidation and corruption of oils and fats in dairy products, and significantly improve the flavor of dairy products. The dosage is generally 0.01% to 0.05%.
(6) Tea polyphenols can be added to various high-fat, high-sugar and easily oxidized baked foods, such as moon cakes, biscuits, bread, instant noodles, etc. It can resist oxidation, resist rancidity, maintain freshness, and improve quality. Tea polyphenols can effectively remove the beany smell of soy products. The dosage is 0.005% to 0.02%.
(7) Tea polyphenols can be added to chewing gum, soft candy, crisp candy, sandwich candy, fruit candy and other candies, which can effectively play its antioxidant and fresh-keeping effects, and have the functions of eliminating bad breath and preventing tooth decay. The dosage is 0.05% to 0.02%.
(8) Tea polyphenols can be added to various beverages, such as soda, cola, ice cream, lemon tea, popsicles, chrysanthemum tea, etc. It can also be added to alcoholic beverages, such as wine, rice wine, sake, and white wine. Adding it to fruit juice can prevent the decomposition and destruction of vitamin C, vitamin A, thiamine and carotene. The dosage is 0.02% to 0.4%.
(9) Tea polyphenols can be added to seasonings, which have the effects of preservation and removal of odor. The dosage is 0.002% to 0.02%.
(10) It can be used as an important ingredient in nutritional health products.
Determination of tea polyphenols content in tea leaves
Tea polyphenols are one of the important chemical components in tea leaves, and their content accounts for about 1/5 to 1/3 of the total dry matter of tea leaves. The flavor, color, and aroma characteristics of finished tea largely depend on the content of polyphenols, and therefore play an important role in the quality of tea leaves.
In tea inspection, the technical measures for detecting its content through chemical reactions are usually potassium permanganate titration and tartaric acid iron colorimetry, taking advantage of the characteristics of tea polyphenols being easily oxidized and producing colored precipitation with high iron salts. The former is a Chinese tea import and export inspection method. It takes advantage of the characteristics of tea polyphenols being easily soluble in hot water and being oxidized by potassium permanganate. 0.1% indigo red solution is added and potassium permanganate is used to titrate twice. First, the total amount of reducing substances in the tea soup is titrated, and then the amount of other reducing substances after removing tea polyphenols is titrated. The difference in the amount of potassium permanganate consumed in the two titrations can be used to calculate the content of tea polyphenols. The tartaric acid iron colorimetric method is a method specified in my country's national standard GB8313-87. It is based on the formation of purple-blue complexes by tartaric acid iron and tea polyphenols. The color depth of the complex solution is proportional to the content of tea polyphenols. Through the colorimetric method, the content of tea polyphenols is expressed by optical density. When measuring, the extinction value E is measured with a 1cm colorimetric cup and a wavelength of 540nm. Calculation: When using 2.5g of green tea sample, the total amount of tea polyphenols (wet state) % = 85.6 × E, and when using 5g of black tea sample, the total amount of tea polyphenols (wet state) % = 42.8 × E. The conversion coefficients 85.6 and 42.8 in the formula can be corrected according to pure tea polyphenols or by KMnO4 titration.
Identification test
Take this product and prepare a 1% aqueous solution. Add a drop of vanilla hydrochloric acid solution (1g vanilla is dissolved in 100ml concentrated hydrochloric acid, prepared when used), and it will appear cherry red.
Toxicity
LD50 (2496±32) mg/kg (rat, oral). More than 95% of the fine products are 3.94 g/kg (rat, oral).
Mutagenicity test Ames test, bone marrow micronucleus test and bone marrow cell chromosome aberration test showed that there were no adverse effects within the concentration of 1/20 LD50, and no side effects.
Dogs were fed with 20 to 40 times the adult dose for 3 months, and all blood indicators and urine tests were normal.
Lifelong feeding of fruit flies and feeding experiments with mice showed that there were no adverse effects on the growth, development and lifespan of fruit flies and on the hemoglobin, red blood cell count, white blood cell count, thymus, spleen cell count, liver volume and body weight of mice.
Usage limit
GB 2760-1996 (g/kg): 0.1 for oily sauces; 0.3 for meat products and fish products; 0.2 for cakes, fried foods and instant noodles; 0.4 for oils, ham, cakes and their fillings. Calculated based on catechins in oils and fats.