Tannins for food preservation and human health: A review of current knowledge

Abstract

Tannins are a type of organic compound commonly found in various plant-based foods and beverages. The majority of species in the plant kingdom comprise tannins, which serve as a defense against predators. Tannins also play a role in regulating plant growth and development, while having a protective function against ultraviolet radiation. The phenolic structure of tannins has also the potential to be used in food, nutraceutical and pharmaceutical industries.

Tannins exhibit a high level of biological activity. Therefore, a number of advantages such as antioxidant, anticancer, anti-allergic, and antimicrobial properties, have been verified in recent research. Thus, they are widely used in the pharmaceutical, nutraceutical and food industries. In addition, the use of tannins as film and coating matrices, antimicrobial and antioxidant agents can enhance the quality of food. However, extraction and purification of tannins are challenging owing to their strong polarity, large molecular weight and complicated structure. Various advanced methods can be employed for the extraction and purification of tannins, depending on the source material and desired application, including solvent extraction, chromatographic methods, super critical, ionic liquid assisted microwave, infrared-assisted extraction technique etc. In particular, supercritical fluid extraction, using CO₂ under specific pressure and temperature conditions, is gaining popularity due to its eco-friendliness and efficiency. This review presents structure and classification of tannins, their extraction techniques, potential properties of tannins as a preservative agent and possible health benefits of tannins with clinical trials.