Tannic Acid

Introduction

Tannic acid is one type of tannin and these two terms are used “interchangeably”. A “tannic acid” is a form of "tannin" and "one type of polyphenol". It can be used in “the food industry and medical field”. It can cause damage to the "eye, skin and even to the respiratory system". Tannins are the basic ingredients for the “chemical staining of woods”.

What is Tannic Acid?

“Tannic acid” can be defined as a “type of polyphenol” and it is an “organic molecule”. The chemical formula that can represent tannic acid is “$\mathrm{C_{76}H_{52}O_{46}}$”. It can be referred to as the “Acidum tannicum or Gallotannic acid”. By nature, it is a “weak acid” and in nature, it can be found in “tara pods, Quercus infectoria, Sicilian Sumac leaves and gallnuts from Rhus semialata”. “The tannins” that are obtained from those, are considered “the tannic acid”.

It also has many types of phenol groups. Sometimes “the extract of oak and chestnuts are also referred to as tannic acid”; however, it is an incorrect use of the term. Tannic acid is one of the “main components of tea and coffee”. Black tea has the highest concentration of tannic acid, while green tea has the lowest.

Types of Tannic Acid

The term tannins are derived from the "Celtic word that is used for oaktree", there was a time, when it was mainly used in the processing of "leather". Tannic acid has two major types and they are-

• Condensed tannins

• Hydrolyzable tannins

Properties of Tannic Acid

Tannic acid has a chemical formula, that is “$\mathrm{C_{76}H_{52}O_{46}}$” and it has many specific properties that make it different from other-

• “The molar mass or the molecular weight” of “tannic acid is 1701.19 g/mol”.

• The “density of tannic acid is 2.12 g/cm3”.

• “Melting point of tannic acid is 200oC” when it is decomposed.

Figure 1 − Structure of Tannic Acid

• pKa of the tannic acid is ca. 6.

• It is slightly acidic.

• It shows a “precipitated nature when reacting with the proteins, amino acids and alkaloids”.

Use of Tannic Acid

"Tannic acid" can be used in many sectors and many forms. The most common use of it is-

• It is used in the making of “albumin tannate”. This is used as the “antidiarrheal agent”.

• In the food industry, tannic acid plays a major role, as it is used as the "colour stabilizer, and as taste enhancer".

• In “the process of dyeing the cellulose fibres” tannic acid is used.

• In rubber manufacturing, it is used.

• It is used as a “reagent” in “analytical chemistry”.

• “In the conservation of ferrous metal objects” tannic acid took a major part in “inhibiting the corrosion”.

Effects of Tannic Acid

Tannic acid shows two different effects on the environment and humans.

• Effects on the environment − Tannic acids are derived from nature but it has a very negative effect on the environment. Excessive use of tannic acid makes a bad impact on the changing of environment as an organic matter. The “solution of tannic acid and water”, which is commonly known as “cola water”, reduces the pH level. As a result, it makes “the environment more acidic”, which affects all the organisms that stay around.

• Effects on Humans − The “effects of tannic acid” are mainly positive but have some “negative or hazardous effects” too. It is used in “controlling bleeding, reducing the condition of soreness” and is to cure “throat infections”. However, if it is used for the long term it can affect negatively. It affected the eyes and respiratory system and damage it, skins also affected by it, and it creates nausea and diarrhoea.

Difference between tannic acid and tannins

Tannic Acid	Tannins
Tannic acid is one of the most important “organic molecules, which can be represented with the “chemical formula of $\mathrm{C_{76}H_{52}O_{46}}$”.	Tannins are a group of "polyphenols" it can "bind with the proteins" and can "precipitate them".
It is a weak acid, which contains "many phenol groups".	It occurs in plant tissue, and is "a class of organic molecules".
It can be applied to "woods to react with chemical stains" and is very useful in beer and wine clarification".	It can be used in “tanning leather, and in the making of anticorrosive”.

Table 1 − Difference between Tannic and tannins

Conclusion

The “positive effects and use of tannic acid are endless”; however, the most important fact about it is that it plays a crucial role in “modern-day medical science”. “Tannic acid” is specially used for the dyeing of "cellulose fibres", such as "cotton". It can be combined with "alum and with iron". Other than that, "the use of tannic acid in humans is vast", but the negative effects cannot be ignored.

FAQs

1. Why are tannins injurious to the skin?

Tannins are not injurious rather they have “anti-inflammatory properties” that are believed to be useful to humans. It can work on the “redness and inflammation” and minimize the effect.

2. What kind of food has tannic acid?

There are ripened fruits that contain tannic acid, such as “grapes and pomegranates”. Other than these two, there are some “berries, nuts, squash, chocolates”, that have “tannic acid”.

3. What is “the main use of tannins”?

Tannins are mainly used in painting, other than that, it is used in “tanning leather, dyeing as mordants, and precipitating proteins from the wine and beer in clarifying process”. In the medical field, it is used as the “astringent in medicine”.

4. In between tea and coffee, which has more “tannic acid”?

Tea and coffee, both have tannins as “one of the main active elements”. The percentage of “tannic acid in coffee is 4.6, whereas in tea, it is almost 11.2 %”. Black tea has the “highest concentration” of “tannic acid which is near 11.76 to 15.14%”.