Gas Transmission Rates of Unperforated and Perforated Polyethylene Films for Modified Atmosphere Packaging Applications
Ibn Xavier R. Malilay1, Kevin F. Yaptenco2, Arnold R. Elepaño3, and Edgardo V. Casas4
ABSTRACT
Oxygen and carbon dioxide transmission rates (OTR and CO2TR, respectively) of low-density polyethylene (LDPE) films were measured at 5, 10, and 26oC (ambient condition) using an exponential decay method. Commercially available LDPE films with a nominal thickness of 25, 40, and 50 μm were used; transmission rates of unperforated film samples were measured first, followed by measurements when samples were perforated once with a 1.10 mm cold needle. Values for OTR and CO2TR of unperforated film samples decreased at lower temperatures and as film thickness increased. The effect of temperature followed Arrhenius kinetics (R2 > 0.920); activation energy (Ea) for OTR and CO2TR had a range of 20.9-32.6 and 18.8-35.1 kJ mol-1, respectively. Perforations made with a cold needle were roughly rectangular and had an average length, width, and area of 731 μm, 71 μm, and 51,695 μm2, respectively; corresponding diameter of a circular perforation with an equivalent area was 256 μm which was considered as a macro-perforation. Gas transmission tests showed that as film thickness and temperature increased, OTR and CO2TR through individual perforations tended to decrease. The temperature effect could be due to distortions in the film at different temperatures. OTR and CO2TR per perforation had a range of 703-1,146 and 337-896 mL d-1, respectively. Calculations based on the respiration rate of ‘Lakatan’ banana at 28oC showed that a transport package of this banana variety (13 kg) could be kept at 28oC and 5% O2 using 38.1-mm PE film without perforations. For bulk storage of 240 kg of the same variety, however, an impermeable plastic tent provided with perforated diffusion windows would require 64 perforations at 28oC to maintain the required level of O2.
Keywords: gas transmission, perforated, polyethylene film
Abbreviations: Ea – activation energy; MAP – modified atmosphere package; CO2TR – CO2 transmission rate; OTR – O2 transmission rate
1 BSAE Graduate, Agricultural and Bio-Process Division (ABPROD), Institute of Agricultural Engineering (IAE), College of Engineering & Agro-Industrial Technology (CEAT); 2Associate Professor, 3 Professor, and 4University Researcher II, ABPROD, IAE, CEAT, University of the Philippines Los Baños, 4031 College, Laguna, Philippines.