Oxygen Transmission Rate

The oxygen transmission rate (OTR) was determined by measuring the oxygen partial pressure over time inside a stoppered BCT with a Mocon (Brooklyn Park, MN) OpTech system.^11,12 An oxygen sensor was affixed to the interior of a BCT. The BCT was sealed with epoxy and a glass slide under a reduced oxygen atmosphere (nominally 0.2% oxygen). Once the epoxy was set, the initial atmospheric composition within the BCT was measured. The BCTs were stored in a controlled temperature chamber at 25 °C. As the oxygen content within the BCT increased over time, the intensity of the light emitted by the sensor decreased in accordance with the Stern-Volmer relationship¹² for fluorescence. The oxygen partial pressure, pO2,t was measured once each day over the course of 7 d. Experimental plots of ln(pO2,outside−pO2,t)vst were linear, with the slope equal to the oxygen transmission rate constant of the BCT. The OTR constant, in units of day^–1, was a convenient metric that was used to calculate the permeation rate, in units such as cubic centimeters of oxygen per day per package under specified conditions. The lower limit of detection of the OTR test instrumentation was 0.00006 day^–1.