Approach tannic acid with a scientific mindset—understand it, and harness its benefits effectively.

There are several methods for detecting tannic acid, including the skin powder method, high-performance liquid chromatography, UV spectrophotometry, and gas chromatography. Tannic acids from different sources exhibit vastly varying chemical structures and compositional contents. Consequently, the sensitivity and stability of each detection method can differ depending on the specific tannic acid product being analyzed.

Chestnut tannin is best suited for the peel powder method (LY/T1082-2008; European method ISODIS 14088), which was selected by the International Association of Leather Chemists from numerous recommendations and has since gained widespread acceptance among peers worldwide. This method is highly stable and offers excellent repeatability. However, its main drawback is that it requires a relatively lengthy and complex procedure.

The UV method (LY/T1642-2005, GB/T27985-2011) is suitable for gallic acid tannins, offering simple operation and rapid detection. However, the results can be easily influenced by impurities, making it practical when high accuracy is not strictly required.

The HPLC method for detecting tannic acid offers high resolution and sensitivity in impurity analysis, but to date, there is no comprehensive national standard in place. When analyzing different tannic acid products, careful attention must be paid to selecting appropriate mobile phases, optimizing their ratios, controlling flow rates, and managing column temperature conditions.

We know that tannic acid has an astringent, bitter taste—even hydrolyzed tannic acid retains its harsh, puckering flavor, which can discourage feed intake and reduce the activity of digestive enzymes. This is also closely related to tannic acid’s strong affinity for proteins. That’s why we apply a coating treatment to the tannic acid. After coating, however, the conventional detection methods mentioned earlier can no longer be used directly. Instead, we need to heat the sample in a boiling water bath to dissolve the coating shell, followed by a pre-treatment step before proceeding with the actual content analysis.

The coating of tannic acid is primarily designed to mask its bitter taste, preventing it from reducing animals' feed intake. It also aims to minimize the contact between tannic acid and digestive enzymes, thereby preserving enzyme activity. That’s why the Kangdequan Coating Research Institute, which has spent over five years studying tannic acid coating technology, emphasizes that coated tannic acid not only needs to eliminate bitterness during oral chewing but also must provide controlled, sustained release. By releasing gradually and evenly throughout the digestive tract, the coating ensures that large amounts of tannic acid don’t come into sudden, intense contact with digestive enzymes—preventing unwanted reactions that could otherwise impair digestion.