Assessment of the risk of physical contamination of bread packaged in perforated oriented polypropylene films : measurements, procedures and results

Perforated films used for wrapping factory-manufactured bread must permit a very rapid and intense moisture exchange because the packaging operation is carried out while the bread is still warm (about 80°C) and releasing a high quantity of moisture. The open surface of the wrapping of those products sold in self-service retail outlets generates suspicion about possible contamination of bread not properly handled by the consumers and a better knowledge of the performance of these materials seems appropriate. Using two different approaches, the geometrical characteristics and perforation pattern of 13 different oriented polypropylene (OPP) films representative of the whole European market were assessed objectively. All the measured parameters (density of perforation, hole dimension, open surface, etc.) showed asymmetric distributions, i.e. with averages close to the lowest figures. Similar asymmetric distribution was shown from the 'risk of contamination' by artificial sweat and saliva: an empirical parameter which was measured by procedures developed to simulate the worst possible case of inappropriate manipulation of the packed bread. Good correlation was found between the 'risk of contamination' and both the 'hole surface' (mm2) and the 'open surface' (percentage holes surface/film surface), leading to the conclusion that the proposed procedures could represent useful methodologies for assessment of such a particular case of possible food contamination.