What is the Difference Between Tannin and Tannic Acid

The main difference between tannin and tannic acid is that the term tannin is used to name a group of organic compounds, whereas tannic acid is a type of tannin.

Tannins are organic compounds that fall under the category of polyphenols. These compounds contain several phenol groups in the same molecule. Tannic acid is a special type of tannin. Tannins occur mainly in plant tissues; therefore, we can name them as polyphenol biomolecules.

Key Areas Covered

1. What is Tannin 
     – Definition, Properties, Uses
2. What is Tannic Acid
     – Definition, Properties, Uses
3. What is the Difference Between Tannin and Tannic Acid
     – Comparison of Key Differences

Key Terms

Tannin, Tannic Acid, Polyphenol

What is Tannin

The term tannin refers to a group of polyphenols that can bind with proteins and precipitate them. These are organic compounds that can react with amino acids and alkaloids. Also, these tannins are well-known as astringent compounds. Furthermore, these compounds occur in a wide variety of plant tissues. They play an important role in providing protection to the plants from predation and help the regulation of plant growth. Besides, tannins occur in unripe fruits; astringency of tannins cause their dry and pucker felling.

Moreover, tannins can be classified into three major groups: hydrolyzable tannins, phlorotannins and condensed tannins. All these groups of tannins are polymeric structures with monomer units. That is; the monomer of hydrolyzable tannins is gallic acid, and the monomer of phlorotannins is phloroglucinol. Meanwhile, the monomer of condensed tannins is flavan-3-ol. Furthermore, these three classes of tannins have different sources as well. e.g. for hydrolyzable tannins, the source is plants, while the source for phlorotannins is the brown algae; for condensed tannins, the source is heartwood.

Figure 1: General Appearance of Tannic Acid

Besides, there are three types of methods to determine the existence of tannins in a given sample.  They are the alkaloid precipitation method, Goldbeater’s skin test, and ferric chloride test. Here, using the alkaloid precipitation method, it is possible to observe alkaloids precipitating tannins and other polyphenols. Also, we can use this method as a quantitative analysis, as well. In Goldbeater’s skin test, the goldbeater’s skin is dipped in hydrochloric acid and rinsed in water; this is followed by treatment with ferrous sulfate solution. And, this test gives a blue-black colour if tannin is present.

What is Tannic Acid

Tannic acid is an organic molecule having the chemical formula C₇₆H₅₂O₄₆. It is a special type of tannin that can be named as a polyphenol due to the presence of several phenyl groups. It has a weak acidity; thus, tannic acid is a weak acid. This weak acidity is a result of the presence of several phenol groups.

Figure 2: Chemical Structure of Tannic Acid

Moreover, the tannic acid has many applications. We can use tannic acid as a mordant in the dyeing process in the production of cellulose fibre forms such as cotton. We can also apply tannic acid to wood that has a low tannin content. Furthermore, we can use tannic acid on metal objects to prevent corrosion. In addition to these, tannic acid is useful in the food industry as well; for example, in wine clarification, beer clarification, colour stabilizing, etc.

Difference Between Tannin and Tannic Acid

Definition

The term tannin refers to a group of polyphenols that can bind with proteins and precipitate them, while tannic acid is an organic molecule having the chemical formula C₇₆H₅₂O₄₆.

Properties

Tannin is characterized by the presence of several phenyl groups, astringency, acidity, etc. while tannic acid is characterized by weak acidity, solubility in water, etc.

Uses

Furthermore, tannin plays an important role in providing protection to the plants from predation and helps the regulation of plant growth. Tannic acid, on the other hand, can be applied to wood that is low in tannin, which helps to react with chemical stains, and can be added as a mordent for dye production, etc.

Conclusion

To recap, the tannic acid is a special type of tannin. It is an organic molecule similar to the other members in the group of tannins. Therefore, the main difference between tannin and tannic acid is that the term tannin is used to name a group of organic compounds whereas tannic acid is a type of tannin.

Reference:

1. “Tannin.” Tannin – an Overview | ScienceDirect Topics, www.sciencedirect.com/topics/chemistry/tannin.

Image Courtesy:

1. “Tannin in Plastic container” By Simon A. Eugster – Own work (CC BY 3.0) via Commons Wikimedia
2. “Tannic acid” By Michał Sobkowski – (CC BY-SA 4.0) via Commons Wikimedia