OTR (Oxygen Transmission Rate) is the measurement of the amount of oxygen gas that passes through a material over a given period of time. OTR is measured in either cc/m2/24 hours or cc/100in2/24 hours.
A critical function of flexible packaging is to reduce the effects of oxygen on packaged products. Changes in product color, odor, and taste are the most easily detected effects of oxidation. Nutrient loss, product rancidity and microbial spoilage play an equally important role in product degradation over time and are all controlled, in part, by the presence of oxygen. Reduction or total removal of headspace oxygen along with the prevention of ingress has been shown to minimize the oxidative effects and prolong product shelf life while improving quality.
Testing material samples for OTR properties requires that the test specimen be a clamped or attached to a diffusion chamber. Pure oxygen is then introduced into the upper half of the chamber while an oxygen-free carrier gas flows through the lower half.
Molecules of oxygen diffusing through the sample into the lower chamber are conveyed to the sensor by the carrier gas. This allows a direct measurement of the oxygen.