Introduction
Tannin acid , also known as tannin. Tannin is a light yellow amorphous powder or a shiny scaly or sponge-like solid. It has no special smell, has a bitter taste and has astringent properties. Gradually darkens when exposed to air and sunlight. Soluble in cold water, infinitely soluble in hot water; soluble in methanol, ethanol, acetone and ethyl acetate, insoluble in benzene, ether, chloroform, petroleum ether and carbon disulfide. Tannic acid aqueous solution is weakly acidic and easily oxidized. It oxidizes faster in alkaline solutions and makes the solution darker. When encountering ferric ions, the solution turns blue-black and reacts with gelatin and alkaloids to produce precipitation. It reacts with lead, aluminum, zinc, germanium and other metal ions to form multinuclear complexes, insoluble salts with special colors. Tannic acid decomposes into pyrogallic acid and CO2 when heated to 210-215°C. Tannic acid has low toxicity, but ingesting large amounts can cause vomiting, abdominal pain, diarrhea, and can lead to circulatory system disorders and death. It can decompose at high temperatures to produce pyrogallol and carbon dioxide.
Production method
Tannin is found in the bark and fruits of various trees (such as oak and sumac). It is also the main component of the galls produced by insect attacks on these trees, with a content of 50% to 70%.
Crush the gallnuts to remove impurities such as insect corpses and insect excrement, put them into a copper or wooden extraction tank, extract with soft water, concentrate the extract under reduced pressure, add a small amount of ether, and spray-dry to obtain light tannic acid. . For medicinal tannins, the concentrated solution is extracted with ether, the leachate is bleached with sodium bisulfite, and the ether is recovered to form medicinal tannins.
The gallnuts are crushed and screened, then soaked in water. The soaking water is clarified, preheated, spray-dried, and the dried powder is sieved to obtain the finished product. ;Put 100 kg of refined naphthalene into the sulfonation kettle, raise the temperature to 125°C, add 120kg of concentrated sulfuric acid while stirring, and react at 155~165°C for 6~8 hours. Take a sample and measure the end point. If it is completely dissolved in water, it proves that the sulfonation is complete. Gradually cool down to 110°C and add a small amount of water to dilute. The material is hydraulically poured into the condensation kettle at around 80°C. Add 39kg of 37% formaldehyde aqueous solution dropwise at about 70°C. After the dripping is completed, react at 80~90°C for 3 hours to obtain a bluish-black viscous liquid, which is the finished product. The finished product is obtained by crushing, extracting, purifying, concentrating and drying larch bark.
The function between industrial tannic and medical tannic:
Tannic acid is mainly used as a mordant in dyeing. It is also used to prepare gallic acid and pyrogallic acid. It can also be used to manufacture leather tanning agents, rubber coagulants, protein and alkaloid precipitants, and to measure beryllium, aluminum, nickel, Reagents for copper and other metals. The light yellow to light brown amorphous powder obtained by evaporating and drying the water extract of gallnuts is industrial tannic acid, containing more than 80% of tannic acid, and also contains a small amount of gallic acid, digallic acid, and gallic acid. acid and quintuple acylglucose, etc. Tannic acid is easily hydrolyzed by acids or enzymes, and the hydrolysis products are gallic acid and glucose.
Industrial tannins
The main functions are as follows:
As raw material for gallic acid and pyrogallic acid.
Mordant. Used for fiber fixation or dyeing, as salt-based dye.
Ore flotation agent. Rare metal smelting, extracting germanium from lead-zinc ore or smoke, extracting thorium, polonium and other rare metals from solution, extracting lead and copper from chalcopyrite.
Conversion coating. Aluminum and its alloy plates, steel, copper, zinc surface corrosion protection, etc.
Food additives. Such as food antioxidants, beverage clarifiers, premium inks and printing inks.
Drilling mud diluent.
Synergist. Referred to as TMP or sulfonamide synergist.
Deodorant. Used to remove ammonia and other odors in refrigerators, warehouses, and toilets.
Medicinal tannins
Medicinal tannins can be used to synthesize medicines for heart diseases such as crotondiamine and crotonzolin; to synthesize diphenyl diester to treat hepatitis B; to synthesize antimony-273 to treat schistosomiasis. Tannic acid can inhibit bacterial growth and absorption of intestinal toxins, and can be used to prevent and treat diarrhea. Medicinal tannins can be directly used in beverages, frozen products, candies, ice cream, and meat products; used as burn and scald wound astringents and gastrointestinal hemostatic agents to prevent infection; and can be made into tannin glycerin, tannic acid protein, and tannic acid. Ointments, anti-cold agents (N-diamidinomorpholine tannins), health promoters, insect repellents, insecticides, radiation protection agents, contraceptives and special toothpaste, etc.
Application
Tannins in wine
Tannin is one of the two phenolic compounds contained in wine, especially in red wine. The skin and seeds are removed during the brewing process of white wine, which contains less tannin. Tannins are beneficial in the prevention of cardiovascular disease. The tannins in wine are generally obtained by soaking and fermenting grape seeds, skins and stems, or by extracting the tannins in oak due to their storage in oak barrels. The amount of tannin can determine the flavor, structure and texture of a wine. Red wines that lack tannin have a light texture without a thick feeling, such as Beaujolais red wine. Tannin has antioxidant effects, and tannin-rich red wine can be stored for many years and gradually develop a mellow and delicate aging flavor. The tannins contained in the wine will make the mouth feel dry and the oral mucosa will feel wrinkled after the wine is tasted.
Tannins in animal feed
As a type of polyphenolic compound, tannic acid is widely present in plants and has various biological activities such as antibacterial, antiparasitic, antiviral, antioxidant, anti-inflammatory, and immune regulation. Therefore, tannins are the main research direction for natural alternatives to antibiotics in feed. Plant tannins have strong protein affinity and have been successfully used in ruminant nutrition to reduce rumen protein degradation, thereby improving protein utilization and animal production efficiency. Adding tannin-containing feeds to ruminant diets also has three important functions, namely controlling gastric bloating, intestinal parasites and pathogenic bacteria in animals. Tannins have traditionally been considered an "anti-nutritional factor" in monogastric animals and poultry, but some studies have shown that when used appropriately, tannins improve the intestinal microbial ecosystem and enhance intestinal health, thereby increasing production. performance. The suitability of phytotannins as alternatives to antibiotics in feed depends on many factors that contribute to the large variability in their observed effects.
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