Technological Application of Tannin-Based Extracts

Abstract

Tannins are polyphenolic compounds naturally found in vegetables. Their presence in nature has prompted their historical use in many different ways. The revision of their traditional utilization has allowed their further modification aiming for an industrial application. Sometimes these modifications have implied the addition of harmful substances such as formaldehyde, classified as a carcinogen of category B1. In other cases, these natural tannins have been replaced by synthetic compounds that threaten human and animal health and damage the environment. Therefore, currently, both academy and industry are searching for the substitution of these unsafe complexes by the increasing inclusion of tannins, natural molecules that can be obtained from several and diverse renewable resources, modified using harmless additives. To achieve promising results, cost-efficient and eco-friendly extraction methods have been designed. Once these green alternatives have been isolated, they have been successfully applied to many fields with very assorted aims of utilization such as coagulants, adhesives, floatation agents, tannings, dyes, additives, or biomolecules. Therefore, this review offers a global vision of the full process that involves the tannin's technological application including an overview of the most relevant tannin sources, effective extraction methods, and their utilization in very diverse fields.

Keywords: additives; human and animal health; industrial application; natural molecules; tannins; traditional utilization.

Figure 1

Chemical structure of common molecules found along with the tannins class. (A) Galloyl unit, (B) penta-O-galloyl-beta-d-glucose (PGG), (C) hexahydroxydiphenic acid, (D) phloroglucinol, (E) catechin and gallocatechin, (F) epimers of catechin and gallocatechin.