Implementation of transglutaminase 2 as a crosslinking agent for salivary oral models: Effects in (in)soluble complexes formation and compound adsorption with different polyphenol families

Astringency, a trigeminal sensation common in polyphenol-rich foods, involves two mechanisms: salivary protein precipitation (M1) and polyphenol adsorption onto mucosal or epithelial surfaces (M2). This study investigates the role of transglutaminase 2 (TGM2) in enhancing mucosal pellicle formation and influencing these mechanisms. Oral cell-based models were optimized using three TGM2 titers and two incubation times, identifying 0.2 U.mL^-1 as optimal for significantly increasing cross-linked proline-rich proteins, statherin, and P-B peptide. Optimized models were exposed to tannic acid (TA, hydrolysable tannins) and grape seed extract (GSE, condensed tannins). In whole saliva (WS) models, M1 was the dominant interaction, particularly for TA (74 %-83 %) versus GSE (40 %-44 %). In saliva-free conditions, TA showed stronger adsorption (M2), with up to a 12.8-fold increase over M1. GSE exhibited minimal M2 interaction. These results highlight how astringency mechanisms differ by compound and oral environment, offering a refined model for studying molecular interactions and sensory effects of polyphenols.