Ambient Oxygen Ingress Rate MethodÐAn Alternative Method to Ox-Tran for Measuring Oxygen Transmission Rate of Whole Packages By Hanne Larsen,* Achim Kohler and Ellen Merethe Magnus MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 A Ê s, Norway The ambient oxygen ingress rate method (AOIR) is an alternative method to Ox- Tran for measuring the oxygen transmission rates (OTR) of whole packages. The objective of the present work was (a) to compare OTR values obtained by the two methods, and (b) to evaluate the use of the AOIR method for measuring OTR at realistic food storage temperatures and humidity levels. The AOIR method gave equal OTR values compared to the Ox-Tran method for the ®ve different types of whole packages used in the experiment, with OTR values in the range 0.06±1.48 ml O 2 /day. The repeatability of the AOIR method measured on an HDPE bottle was 2.6% of the measured value in this experiment. This is slightly higher than the general speci®cations of the Ox-Tran method (1% of reading for packages). However, the AOIR method can be considered to be a reliable, precise and cheap alternative method to the Ox-Tran method for measuring OTR of whole packages. The capacity of the method is also high. The AOIR method showed satisfactory results when comparing OTR for packages tested under realistic food storage conditions covering 23°C/50% relative humidity (RH) and at 4°C/60% RH on the outside, combined with water (100% RH) or dry air inside the packages. Copyright O 2000 John Wiley & Sons, Ltd. Received 29 September 2000; Accepted 30 September 2000 KEY WORDS: method; oxygen transmission rate; permeability; whole packages INTRODUCTION The shelf-life of many foods is determined by the oxygen transmission rate (OTR) of the ¯exible ®lms and containers used in packaging, especially during long-term storage. Many different tech- niques for measuring OTR of ¯at ®lms have been developed through the years. 1±5 Today, the ASTM- approved method using a dynamic permeation cell (¯owing gas systems) with a sensitive oxygen- speci®c coulometric detector is the method of greatest commercial use. A commercial instru- ment, which conforms to the ASTM method, is the MOCON Ox-Tran apparatus (Modern Controls Inc. Minneapolis, MI, USA, hereafter referred to as the Ox-Tran method). Converting the ¯at material to a ®nished package usually changes the package permeation compared to the ¯at material. 6 By measuring OTR for the whole package, any changes due, for example, to the stretching of the material, heat seals and possible defects created under the converting process are taken into account. It is therefore recommended that the ®nished package should be tested under expected ®eld temperature, barometric pressure and rela- tive humidity conditions. 6 The MOCON Ox-Tran PACKAGING TECHNOLOGY AND SCIENCE Packag. Technol. Sci. 2000; 13: 233±241 Copyright  2000 John Wiley & Sons, Ltd. * Correspondence to: H. Larsen, MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 A Ê s, Norway. E-mail: hanne.larsen@matforsk.no