*2.4. Water Vapor Transmission Rate (WVTR)*

During storage of packaged fruit, moisture moves across films by diffusion force because of a concentration gradient created on opposite sides of the film. A modification of the dry cup technique (ASTM, 2005 method E96-95) was used to determine WVTR gravimetrically, as described by Opara et al. [27]. Film samples were cut out from areas of no-perforation on the liners in order to test for vapor transmission across the liner surface. Transmission across perforations was also assessed, and in this case film samples having one perforation at the centre were cut out from the macro-perforated liners (2 mm HDPE and 4 mm HDPE). The experiment was carried out in triplicate. Aluminium test cups were filled with 8.0 ± 0.5 g of anhydrous CaCl2 salt. The cups were fitted with an O-ring and grease to provide proofing against moisture and air. A film sample was then laid on top and the cup tightly closed giving an active surface area of 25 cm2. Cups were weighed and stored in sets under different conditions: 20 ◦C, 65% RH and 5 ◦C, 90% RH. The WVTR (g m−<sup>2</sup> d<sup>−</sup>1) of films were calculated on the basis of mass of water gained by CaCl2 salt in the cup over time.
