Assessment of Penicillium expansum and Escherichia coli transfer from poplar crates to apples

Poplar crates are widely used in contact with foodstuffs. One of the major markets for poplar crates is apple packaging. As a direct food contact material, wood is subject to European regulation n° 1935/2004, which requires no negative effect of material or packaging on foodstuffs. This study aims to quantify the transfer of Penicillium expansum conidia and Escherichia coli from poplar specimens to Golden apples. This [microorganisms-poplar-Golden apple] model was developed taking into account realistic parameters with extreme and usual conditions. Poplar specimens were artificially contaminated with P. expansum and E. coli. They were then put in contact with apples and stored in a climatic room for up to one week. Both wood specimens and apples were analyzed to assess the survival of microorganisms on wood specimens and the proportion of microorganism transfer to apples. Whereas P. expansum conidia survived but did not grow on wood specimens, E. coli mortality was observed after one hour of contact with wood. The proportion of both microorganisms transferred to apples was less than 0.25%. The impact of wood moisture content, contact time between wood and apples, and apple supply variability on the transfer levels were studied. The hygroscopic properties of wood were discussed. The low and reproducible transfer levels observed demonstrate that poplar is a safe packaging material for apples.