Gallnuts from oak and sumac contain the highest naturally occurring level of tann (gallotannin): 50-75%. They also contain 2-4% each of the smaller molecules gallic acid and ellagic acid (see structures next page) that are polymerized to make tannins. The tannin of gallnuts has been used for centuries for tanning of leather (a process involving coagulating proteins). Now, gallnut extracts are widely used in pharmaceuticals, food and feed additives, dyes, inks, and metallurgy. Gallotannin (comprised of molecules of gallic acid attached to a central glucose) is obtained from natural gallnuts by extraction with hot water; gallic acid is obtained by the hydrolysis of tannic acid with sulfuric acid. When heated above 220°C, gallic acid loses carbon dioxide to form pyrogallol; other chemicals in demand, such as propyl gallate, octyl gallate, dodecyl gallate, syringic acid, and trimethoxybenzoic acid, can all
be made from gallnuts.
There are additional sources of these desired components. Since 1989, Chinese manufacturers of gallnut products began using tara (spiny sappan; Caesalpinia spinosa) imported from Peru for production of gallic acid. While sappan heartwood (fromCaesalpinia sappan) is used in Chinese medicine as a blood vitalizer, tara is an extract from the fruits pods of the related C. spinosa. The tannin concentration is high in the pods; a typical analysis is: gallotannin 53.1%, gallic acid 9.5%, ellagitannin 6.9%. The shift to use of tara resulted from over collection of gallnuts in China leading to a high price for them. But, this shift to alternative sources of tannins led to a recovery of gallnut supplies and their reduction in price and restoration as major market items; in addition,Caealpinia spinosa was also cultivated in Southwest China (e.g., Yunnan Province), reducing the need for imports from Peru. Other major sources of tannins are chestnut, mimosa, quebracho, valonea, and myrobalans (fruits and twigs).
♥ Function and application of Gallnut powder:
1. With the function of antioxidant and antimicrobial;
2.It has the effect on improving the body disease-resistant ability, liver and gastrointestinal systemfunction;
3. With the function of treating chronic diarrhea and dysentery
4. With the function of dispelling heat, eliminating irritability, diuretic, cooling blood and detoxification;
5. With the function of enhancing immunity.
6. It is clarifying agent of beer and low alcohol wine. As pharmaceutical raw materials for clearing heat,
anti-inflammation and so on, it is mainly used in pharmaceutical field; Applied in food field, it can be
produced into wine, canned, condensed juice and other more nourishment;
7. As active ingredients of skin care products, it is mainly used in cosmetic industry.
