## 2 Tannin Application
Moreover, the copolymerization of tannins with synthetic adhesives allows for decreased formaldehyde emission from synthetic resins. Other bio-sourced resins and adhesives are also obtained, such as epoxy resins, tannin-furanic and tannin-resorcinol-formaldehyde thermosets, and non-isocyanite and isocyanite polyurethanes. These materials found various applications in tire cords, grinding wheels, angle grinder disks, automotive brake-pad matrices, Teflon coatings, paper impregnation, and many others [34; 35]. Additionally, tannin coagulants and tannin-based adsorbents have been applied in the removal of heavy metals from water and wastewater. Their chemically modified forms can also serve as promising materials for eliminating other challenging water contaminants [36; 37]. Tannins are also widely explored in biobased packaging materials as additives to nanocellulose, starch, and chitosan, significantly improving their antibacterial and antioxidative properties [38]. Tannic acid has also proven an effective crosslinker for casein, gelatin, and other proteins in the production of edible foils for food packaging with an increased stability to oxidative degradation [36; 39; 40]. In feed production, applying tannins in animal food has positive effects on animal intestinal microbiota and gut health, combined with increased animal production. Due to their antibacterial and anti-inflammatory properties, they can also be a good alternative to in-feed antibiotics [41]. The biochemical activity of tannins makes them valuable components of nutraceuticalals, pharmaceuticals, and medicinal preparations as antioxidants, radical scavengers, anti-mutagenic, anti-cancerogenic, hepatotoxicity, and neuroprotective agents (Figure 1) [42]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Plant**} & **Extraction** & **Tannin Content** & **Type of** & **Applications** & **Ref.** \\  & **Method** & **(Plant Part)** & **Tannins** & **Applications** & **Ref.** \\ \hline \multirow{4}{*}{Pine} & \multirow{4}{*}{C} & 35 mg/g (bark) & \multirow{4}{*}{Condensed} & Food and pharmaceutical industry, & \\  & & 51.4 mg/g (bark) & & & & \\  & & 70.4 mg/g & & & & \\ \hline \multirow{4}{*}{Spruce} & \multirow{4}{*}{C} & 70 mg/g & \multirow{4}{*}{Condensed} & Antioxidants, & \\  & & 94.82 \({}^{\text{TFC}}\) mg TAE/g DM (bark) & & & & \\  & 41.6 \({}^{\text{TEF}}\) mg/g DM (bark) & & & & \\  & SFE & 253.64 \({}^{\text{TFC}}\) mg TAE/g DM (bark) & & & & \\ \hline \multirow{4}{*}{Grape} & \multirow{4}{*}{C} & 9.93 mg EE/g (marc) & \multirow{4}{*}{Condensed} & \multirow{4}{*}{Plastic and wood adhesive, [2; 31; 32; 33]} \\  & & MAE & 66.9 mg EE/g (marc) & & & \\  & & C & 25.75 \({}^{\text{TFC}}\) mg GAE/g & & & \\ \cline{1-1}  & & UAE & 20.04 \({}^{\text{TFC}}\) mg GAE/g & & & \\ \cline{1-1}  & & 9.9 mg/g (skin) & & & \\ \cline{1-1}  & & C & 106 mg/g (seed) & & & \\ \cline{1-1}  & & 25 mg/g (stem) & & & \\ \hline \hline \end{tabular}  
* C—conventional extraction; MAE—microwave-assisted extraction; CFW—conventional from waste products; CFS—conventional from spent products; UAE—ultrasound-assisted extraction; M—macretion; SEFFS—supercritical fluid extraction from spent products; SE—soxhlet extraction; CM—cold maceration; DM/DE—dry mass/dry extract; CTC—condensed tannin content; HTC—hydroized tannin content; TTC—total tannin content; TPC—total phenolic content; TEY—tannin extraction yield; TAE—tannin acid equivalent; GAE—gallic acid equivalent; CE—catch equivalent; EE—epjacichen equivalent; EECs—exhausted olive calves; EGE—epjgallocatechin gallate equivalent; CIE—cyanidin 1 equivalent.  
\end{table} 
Table 1: _Cont._The variety of tannin applications makes tannins the fourth most extracted group of biomass components, following cellulose, hemicellulose, and lignin. In 2022, the global tannin market was valued at nearly $2.5 billion, with an expected annual growth rate of 6.2% projected from 2023 to 2030. Most tannins, accounting for 62% of the market share, are used in the tannin industry.