Tannins extraction: A key point for their valorization and cleaner production

Abstract

Tannins are phenolic compounds with considerable abundance in nature. They have attracted significant attention lately owing to their huge variety of potential applications. Accordingly, the tannin-related activity in terms of research has undergone a great boost, especially as green feedstock for materials in several fields. Nevertheless, the extraction process remains as the main bottleneck for their valorization, due to their heterogeneous nature. In the present review, a comprehensive study of the main types of tannins extraction techniques was carried out based on the works from the last 20 years. The literature review was carried through analysis of an initial sample of works followed by snowballing process, obtaining the main extraction parameters of each method. Thereby, the different tannins extraction methods were assessed and their major strengths and weaknesses elucidated. Moreover, a direct comparison between the different techniques was done, leading to the main prospectives for the efficient and clean tannins extraction and production.

Frying stability of canola oil supplemented with ultrasound‐assisted extraction of Teucrium polium

“…In the form of polymeric flavonoids, they have limited to no solubility in water, whereas in oligomeric form, they are water soluble. Within the flavonoids group, condensed tannins are considered as flavanols, since they are composed of flavan‐3‐ol moieties (de Hoyos‐Martínez, Merle, Labidi, & Charrier–El Bouhtoury, ). In this study, total condensed tannin content of Teucrium polium extract was obtained 3.77 mg/g.…”

Tannin‐Adsorbents for Water Decontamination and for the Recovery of Critical Metals: Current State and Future Perspectives

“…Conventional methods involve maceration and infusion, but new methods such as microwave‐assisted extraction, pressurized liquid extraction, and ultrasound‐assisted extraction can bring important advantages such as shorter reaction times and lower quantities of chemicals. A review of extraction methods, major strengths, and weaknesses was recently published …”

“…The procedures should be optimized in a case-by-case approach, depending on the source, the extraction method and the required nature of the extractible compounds (polyphenols, condensed or hydrolysable tannins). [13] Extraction yields generally increase with the polarity of solvents [5] and extractions in ethanol, [11] methanol, [13] and aqueous solution [11] have been successful. Conventional methods involve maceration and infusion, but new methods such as microwave-assisted Sílvia Santos completed the Ph.D. in Chemical and Biological Engineering in 2009, at the Faculty of Engineering of the University of Porto (FEUP), with a thesis supervised by Dr. Rui Boaventura.…”

“…Tannins are natural phenolic polymers found abundantly in bark, wood, leaves, seeds, and fruits of a variety of plant species . Definitions and chemical classification have been discussed in literature . Tannins are generally classified into condensed and hydrolysable tannins.…”

“…[2] Definitions and chemical classification have been discussed in literature. [2][3][4][5] Tannins are generally classified into condensed and hydrolysable tannins. Hydrolysable tannins are mixtures of simple phenols, such as gallic and ellagic acids (Figure 1), and of esters of sugars (mainly glucose), with gallic and digallic acids, and are present in species such as chestnut, myrabolans, tara, valonea, and oak.…”