Chemical Structure and Component Composition
Chemical Structure: Tea Polyphenols is the general term for polyphenolic substances in tea, mainly including several major categories of compounds such as catechins, flavones and flavonols, anthocyanins, phenolic acids and condensed phenolic acids. Among them, catechins are the main components of tea polyphenols, accounting for about 70 - 80% of the total amount of tea polyphenols. Catechin compounds mainly include epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), etc. The molecular structures of these compounds contain multiple phenolic hydroxyl groups, and this structure endows tea polyphenols with many important chemical and physiological properties.
Component Characteristics: The proportion of tea polyphenol components in different types of tea varies slightly. For example, the tea polyphenols in green tea are mainly catechins, especially the content of EGCG is relatively high, which gives green tea strong antioxidant properties. During the fermentation process of black tea, catechins will undergo oxidative polymerization reactions to generate theaflavins and thearubigins and other components. These components also belong to the category of tea polyphenols and endow black tea with unique color and taste.
Physical and Chemical Properties
Physical Properties: Tea polyphenols are usually light - yellow to tea - brown powders or crystals with an astringent taste. They are easily soluble in polar solvents such as water, ethanol, and methanol, and have a higher solubility in hot water, which is the reason why tea polyphenols in tea can be dissolved during tea - making. The solubility of tea polyphenols in different solvents may be affected by factors such as temperature and solvent polarity. Their melting point range is relatively wide, and the melting points of different components are different, generally around 170 - 220ºC.
Chemical Properties: Tea polyphenols have strong reducibility, which is the basis of their antioxidant effect. Its multiple phenolic hydroxyl groups can provide hydrogen atoms to react with free radicals, thereby terminating the free - radical chain reaction and playing an antioxidant role. In addition, tea polyphenols can also form complexation reactions with metal ions, such as combining with iron ions and aluminum ions. This characteristic has certain applications in food preservation and the pharmaceutical field. Tea polyphenols are relatively stable under alkaline conditions, but under acidic conditions, some components may undergo hydrolysis and other reactions.
Application Fields
Food Industry:
Antioxidant: Tea polyphenols are a natural antioxidant and can prevent lipid oxidation and delay food spoilage during food processing. For example, adding tea polyphenols to lipid - based foods (such as edible oils and fried foods) can extend the product's shelf life. In meat products, tea polyphenols can also inhibit the oxidative discoloration of meat and maintain the color and flavor of meat products.
Food Preservation: Tea polyphenols have inhibitory effects on a variety of bacteria, molds and yeasts and can be used for food preservation. For example, soaking fruits in a solution containing tea polyphenols can reduce fruit rot and extend their shelf life.
Flavoring Agent: Because tea polyphenols have a special astringent taste, they can be used as a flavoring agent to adjust the taste of food. In tea - based beverages, chewing gums and other products, the astringent taste of tea polyphenols can be combined with other tastes to create a unique taste.
Cosmetics Industry:
Antioxidant and Anti - aging: The antioxidant characteristics of tea polyphenols make them widely used in cosmetics. It can scavenge free radicals in the skin, reduce skin aging phenomena such as wrinkles and sagging. Adding tea polyphenols to skin - care products such as creams and serums can provide antioxidant protection for the skin and promote skin health.
Anti - inflammatory and Anti - allergic: Tea polyphenols have certain anti - inflammatory and anti - allergic effects. It can reduce skin inflammation and relieve skin allergy symptoms and is helpful for the care of sensitive skin. In sunscreen products, tea polyphenols can also enhance the sun protection effect and reduce the harm of ultraviolet rays to the skin.
Pharmaceutical Industry:
Prevention of Cardiovascular Diseases: Tea polyphenols can reduce blood lipids and inhibit platelet aggregation, which is helpful for the prevention of cardiovascular diseases. Studies have shown that long - term drinking of tea rich in tea polyphenols or intake of tea polyphenol supplements may reduce the risk of diseases such as coronary heart disease and arteriosclerosis.
Antitumor Effect: Some studies have found that tea polyphenols have inhibitory effects on certain tumor cells, and the mechanism may be related to antioxidant and regulation of cell - signaling pathways. However, the application of tea polyphenols in tumor treatment is still in the research stage and more clinical trials are needed to confirm its effectiveness and safety.
Antibacterial and Anti - inflammatory: Tea polyphenols have inhibitory effects on a variety of bacteria and viruses and can be used to treat some infectious diseases. For example, adding tea polyphenols to oral - care products (such as toothpaste and mouthwash) can prevent and treat oral inflammations such as gingivitis and oral ulcers.
Product Specifications and Quality Standards
Product Specifications: The specifications of tea polyphenol products usually include indicators such as purity and catechin content. Purity is generally expressed as a mass fraction, and the purity of common tea polyphenol products is between 80 - 98%. The catechin content is also an important indicator, especially the content of main catechin components such as EGCG, because they are closely related to the quality and efficacy of tea polyphenols. For example, high - purity and high - catechin - content tea polyphenol products are more widely used in the pharmaceutical and high - end cosmetics fields.
Quality Standards: In the food industry, when tea polyphenols are used as food additives, they must comply with national food safety standards, and there are strict regulations on their heavy - metal content (such as lead and arsenic), and microbial indicators (such as total colony - forming units, the number of molds and yeasts, etc.). In the cosmetics and pharmaceutical industries, tea polyphenols need to meet the corresponding product quality standards, including requirements for purity, stability, and safety.
Safety and Precautions
Safety: Tea polyphenols are safe under normal usage doses. It is a natural component of tea, and the long - term history of human tea - drinking also proves its safety. However, for some special populations (such as pregnant women and lactating women), it may be necessary to be cautious when using tea polyphenol supplements, and it is best to do so under the guidance of a doctor.
Precautions: When storing tea polyphenol products, it is necessary to avoid high temperature, humidity and strong light, because these factors may lead to the oxidation and degradation of tea polyphenols and affect their quality and efficacy. When using tea polyphenols as additives or raw materials, it is necessary to pay attention to their compatibility with other components. For example, in cosmetic formulations, tea polyphenols may react with certain metal ions, and appropriate compatibility tests are required.
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