Environmentally friendly temporary anti-mould treatment of packaging material before drying

Abstract

According to FAO – ISPM No 15, in international trade wood packaging material on the basis of sawn timber requires to be heat-treated to avoid spreading of harmful organisms. “Heat-treatment” means a minimum core temperature of the wood of 56° C for a minimum of 30 minutes. ISPM No 15 does not define moisture content and therefore does not include rules for the drying process.

Practitioners report that fresh sapwood, after having undergone a pure heat treatment without any kind of drying, shows a great affinity to fungi (mould and blue stain). Even though the infestation does not affect the strength properties of the wood, it must be considered as an optical and a sanitary problem. An environmentally friendly, cheap and easy to use technique for temporary anti-mould protection of heattreated wood is needed to bridge the time span between sawing, heat treatment and air or kiln drying.

Results derived from laboratory experiments have shown that the heat-treatment affects the elution of the lipid components within pine sapwood. While searching for alternatives to conventional preservation methods, different environmentally compliant agents (particularly aqueous solutions containing sodiumand potassium carbonate) were found to inhibit the germination of mould and blue stain fungi spores on wood packaging material surfaces in a temporary manner. Besides their effectiveness, the usage of these agents to achieving the temporary protection (e.g. for a couple of weeks) is economically feasible and easily applicable in industrial practice. However, drying (either naturally or technically) is indispensable to avoid fungal hazard on the long run. A combination of temporary treatment immediately after sawing followed by a drying-process (long lasting protection) seems to be the most effective method to protect ISPM No 15 treated wood packaging material against mould.