Interaction of different classes of salivary proteins with food tannins

Abstract

Tannins are polyphenolic compounds commonly present in vegetables, fruits and derived products that interact with proteins, namely salivary proline-rich proteins (PRPs). This interaction forms (in)soluble aggregates that are supposed to be at the origin of the astringency sensation but that also influences tannins bioavailability. Therefore, this interaction was studied herein by HPLC and dynamic light scattering (DLS) using procyanidin trimer and PGG (pentagalloylglucose), to obtain information about the relative affinity of the interaction, solubility (both by HPLC) and size of the complexes formed (by DLS). The results show that mainly acidic PRPs (aPRPs) and statherin interact with both tannins, forming a significant quantity of complexes (either insoluble or soluble), while bPRPs (basic PRPs) interact poorly with procyanidin trimer and gPRPs (glycosylated PRPs) only complex with PGG. In general, PGG formed a high amount of insoluble complexes with salivary proteins while procyanidin trimer formed soluble complexes (except for statherin). For PGG, the maximum aggregation and complexes size (~200nm) correspond to the stoichiometric concentration (232μM). For procyanidin trimer, the concentrations used did not allow to reach the maximum of aggregation. These results highlight the influence and mechanisms that different tannins and salivary proteins could present in their interaction, and consequently in the development of the astringency sensation.