Two steaks were placed on a self-absorbent expanded polystyrene
tray (18×27×2 cm) and the total weight of the case-ready unit was
around 400 g. Each tray was overwrapped with a PVC stretch film that
was manually perforated using a toothed wheel, in order to allow free
exchange of atmospheres during gas flushing and not only to ensure
the oxygen permeation inside primary packages after removal from
master bags. Each film had 12 holes with a 0.36±0.07 mm diameter,
for a total perforated area of 0.407 mm2 (density of perforation 1 hole/
40.5 cm2
). Hole sizes were checked through an optical microscope analysis
on ten samples of film after its wrapping (Nikkon Eclipse ME600,
Nikon Instruments spa, Italy).