The rapid disappearance of surface contamination in the timber poses a lesser risk of cross contamination to other non-porous surfaces such as plastics. The porosity of the wood is not a source of microcavities and roughness conducive to the growth of bacteria, as would occur with non-porous materials. In fact, some researchers (Gilbert & Watson, 1971, Ak et al. 1994b; Abrishami et al., 1994) have concluded that the shredded plastic surfaces are harder to clean.
The wood packaging for single use and dry (with a moisture content less than 20%) is not conducive to the propagation or survival of micro-organisms (Ak et al. 1994a, 1994b; Abrishami et al. 1994; Revol-Junelles et al. 2005). Moreover, according to Abrishami et al., 1994 wet wood surfaces have a behavior similar to plastic surfaces, despite the are less absorbent than dry surfaces. Ak also concluded that plastic tables could not be considered more hygienic than wood.
Abrishami et al. (1994) showed that 88% of new cells inoculation in dry wood were attached after 10 min. In fact, it was seen by scanning electron microscopy (SEM) that many bacteria are associated with the dry regions of the cytoplasm of structural and vegetative tissue of the xylem (woody part of the timber).
Gehrig, Schnell, Zürcher and Kucera in 2002 compared the hygienic aspects of wood and polyethylene cutting boards regarding food contaminations. The study compared the hygenic aspects of cutting boards made of wood (european maple, beech and oak) and polyethylene (PE) and the risk of food contamination through Escherichiacoli bacteria contamination. That showed that humid environment affected equally to bacteria colonies whereas drier environment lead to less bacteria in porous wood surface. On all materials a significant decrease of bacteria count was achieved upon manual washing with detergent and brush followed by rinsing under warm water. For wood, an even higher degree of disinfection could possibly be achieved with the microwave method suggested by Park and Cliver (1996).
Schönwälder et al in 2002, and Friedrich et al in 2007, concluded in the possibility that bacteria are transferred into the timber by absorption with no evidence of a subsequent release.
Revol-Juelles et al in 2005 compared the evolution of dry poplar wood crates and glass surfaces contaminated with Escherichia coli or Bacillus cereus spores by impedance microbiology. Whereas physical and chemical properties of the wood greatly and rapidly decreased the number of cells after different contact times, in inert and nonporous materials growth occurred. Wood exhibited growth-inhibiting properties and cells were no longer metabolically active, concluding that the potential for cross contamination of foods stored directly in contact with previously contaminated poplar wood crates is low under experimental conditions.
Moore et al in 2007, refers to a reduction of pollution or proliferation in porous media versus those smooth or nonporous material.
Despite the fact that timber is questioned in meat processing, meat industry defends the use of wood as a cutting surface and preparation of its products.
In fact, Cliver, based on their own investigations and epidemiological evidence, and other partners, concluded that the boards were better than plastic or glass. It was based on data from a case study on Salmonella revealed that those using wooden planks in the kitchen are less than half as likely to contract the disease than those who use plastic or glass.
Cliver concluded that the bactericidal effect of the wood could be a combination of grip and the drying effect on cells.
Chiu et al, Schönwälder et al, Moore et al, Gough et al, and Milling et al, aslo concluded that: the wood surface leads to decreased proliferation of inoculated pollutants than other surfaces, and reduces the survival time of bacteria in wood. This is more evident the higher the pollution in amount and duration is. Schönwälder et al in 2002 concluded that these properties are independent of the age of the wood.
The Danish Technological Institute (www.teknologisk.dk), leading a broader joint research with research institutes in Nordic, German and Switzerland, inoculated bacteria similar to Salmonella Listeria.en Camphylobacter in different species of wood (oak, pine, Nordic fir , beech and ash) in cutting boards, pallets, containers of fish and food packaging, comparatively with plastic and steel, concluding in a superior bactericidal effect of the first.
This study also highlighted special health qualities of pine, not only for its porosity, but for its antibacterial extracts.
Further investigations proved the survival of selected bacteria (Bacillus subtilis and Pseudomonas fluorescens) which are commonly found in meat, in different conditions in the industry. They were tested on brushed beech, oak and ash, as well as untreated pine and fir wood packaging, with reference to plastic and stainless steel.
The study concluded that the wood reduces the bacterial concentration before plastic and steel, and that wood species behave differentially; oak has better performance than the beech or ash, and Scotch pine is better than the fir
See further information on that study “Part report No 10. Wood plastic and steel- a comparison of hygienic properties” Report_No_10