Analysis of valonia oak (Quercus aegylops) acorn tannin and wood adhesives application

Abstract

The coupling of matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry with 13C nuclear magnetic resonance (NMR) is a suitable method for examining the composition of hydrolysable tannins and has been applied to the investigation of valonia oak (Quercus aegylops) acorn tannin extract. Such methods can determine the extract's structural aspects and other characteristics. It was determined that valonia oak acorn tannin extract is composed of mainly pentagalloylglucose structures; their rearrangement structures, vescalagin/castalagin (with linkages to flavogallonic acid) and vescalin/castalin; ellagic acid and vescavaloneic/castavaloneic acid; and free gallic acid and glucose. Traces of catechin gallate were also observed in this tannin extract. The tannin from acorns of valonia oak was used to substitute up to 50% of the phenol used in the preparation of phenolic resins as adhesives for wood particleboard. These phenol-tannin-formaldehyde resins showed comparable performance to phenol-formaldehyde resins.