22 The Philippine Agricultural Scientist Vol. 90 No. 1 (March 2007) Gas Transmission Rates of Polyethylene and Polypropylene Films K.F. Yaptenco et al. THE PHILIPPINE AGRICULTURAL SCIENTIST ISSN 0031-7454 Vol. 90 No. 1, 22-27 March 2007 Gas Transmission Rates of Commercially Available Polyethylene and Polypropylene Films for Modified Atmosphere Packaging Kevin F. Yaptenco 1* , Ji Gang Kim 2 and Byung Seon Lim 2 Funded by the Postdoctoral Course Program, National Horticultural Research Institute – Rural Development Administra- tion (NHRI-RDA), South Korea 1 Postharvest and Seed Science Division, Crop Science Cluster, College of Agriculture, University of the Philippines Los Baños, College, Laguna 4031, Philippines 2 National Horticultural Research Institute – Rural Development Administration, Suwon, South Korea * Author for correspondence; e-mail: kfyaptenco@yahoo.com; Tel. (49) 536 – 2444; Fax (49) 536 – 3259 Oxygen transmission rates (OTR) of low-density polyethylene (PE) and polypropylene (PP) films were measured at 10, 15 and 17 o C using the whole-bag method of Moyls (2004) for unperforated films. PE films with a nominal thickness of 30, 40, 60 and 80 µ µ µ µ m (PE30, PE40, PE60 and PE80, respectively) were analyzed; thickness of the PP film was 40 µm. Oxygen and CO 2 transmission rates (CO2TR) of 35-µm micro-perforated polypropylene (MPP) were measured at 10, 15, and 17 o C using the method de- scribed by Ozdemir et al. (Ozdemir I, Monnet F, Gouble B. 2005. Postharvest Biol Tech 36:209-213). Temperature effects on unperforated PE and PP films followed Arrhenius kinetics (R 2 > 0.970). Activa- tion energy (E a ) of PE film had a range of 28.1–35.0 kJ mol -1 ; for PP film, E a was 38.1 kJ mol -1 . In general, E a of PE film increased as film thickness (t F ) increased. Q 10-Tr values at 10–20 o C for PE and PP were 1.50–1.66 and 1.74, respectively. Temperature had no definite effect on OTR and CO2TR of MPP. Mean OTR and CO2TR for MPP were 10,848 and 9,554 mL m -2 d -1 , respectively. The average perforation diameter (D mp ) and density (d mp ) was 41.0 µm and 125 perforations per m 2 , respectively, for a 20 cm x 28 cm bag. Comparisons with published data showed the sample film to have gas transmission rates at the lower end of the range for such types of packaging film. Key Words: gas transmission, micro-perforated, modified atmosphere, packaging Abbreviations: A mp – area of micro-perforation, CV – coefficient of variation, d mp – micro-perforation density, D mp – diameter of a micro-perforation, E a – activation energy, MAP – modified atmosphere package/ing, MPP – micro-perforated polypropylene, NHRI – National Horticultural Research Institute, PE – polyethylene, PP – polypropylene, PS – permselectivity, RDA – Rural Development Administration, CO2TR – CO 2 transmission rate, OTR – O 2 transmission rate INTRODUCTION Modified atmosphere packaging (MAP) of fresh or fresh- cut fruits and vegetables commonly involves enclosing the commodity in a package and generating an internal atmosphere passively (using the natural respiration of the product to deplete O 2 and increase CO 2 levels) or actively (by flushing the package with a gas mix with the desired proportions of O 2 and CO 2 ). To achieve the desired results of MAP, the respiration rate of the commodity and film transmission rates of O 2 and CO 2 must be known accu- rately at the optimum storage conditions. This allows a package to be selected based on its gas transmission rates, given the commodity requirements and a realistic combi- nation of fill weight and package dimensions. For commodi- ties with elevated respiration rates (e.g., fresh cut prod- ucts), high gas transmission rates are required that are of- ten beyond the capabilities of ordinary MAP films. For such applications, micro-perforated and micro-porous films are more appropriate. Permselectivity (PS) is defined as the ratio of CO 2 transmission rate (CO2TR) to O 2 transmission rate (OTR). Since micro-perforations have a theoretical PS ratio of 1.0, overall PS of a film can be adjusted simulta- neously with increased gas exchange (Exama et al. 1993). However, when density of perforations is sufficiently high, O 2 and CO 2 are exchanged through the film at similar rates. This results in low O 2 levels (1–5%) accompanied by high CO 2 levels (15–20%). Therefore, only commodities that can