Chitosan–caffeine formulation as an ecological preservative in wood protection

Nowadays, taking into account environmental degradation, climate changes, as well as, environmentally friendly regulations and increasing ecological awareness of consumers, methods of wood protection without negative impact on the environment are being intensively developed. In this study, a mixture of chitosan and caffeine was proposed as ecological wood preservative. The aim of the research was to evaluate the application of chitosan (medium and high molecular weight) as an agent limiting the leaching of caffeine from the structure of treated wood. The resistance of pine wood treated with chitosan–caffeine preparations and ingredients of these preparations (caffeine and chitosan) to brown rot fungus—Coniophora puteana was assessed. The degree of caffeine leaching from the treated wood was determined by chromatographic analysis (caffeine concentration) and elemental analysis (nitrogen concentration). The results showed that chitosan limited caffeine leaching from wood, which was confirmed by chromatographic analysis and changes in the wood structure observed in FTIR spectra. Moreover, wood treated with chitosan–caffeine preparations showed resistance against C. puteana (mass loss about 0.5%); however, antifungal activity was reduced when treated wood was subjected to leaching with water (mass loss about 10%). The obtained results suggest that the chitosan–caffeine preparations can be promising ecological preservatives for the wood treatment.