OTR – Oxygen and Aroma Barrier

The abbreviation OTR stands for “Oxygen Transmission Rate” and indicates how much oxygen diffuses through a material per unit of time. The lower the stated value, the better the protection against oxygen ingress. It is commonly expressed in cm³/m²/day. In practice, the main purpose is to protect the product against oxidation (for example rancidity, aroma changes, colour degradation, or vitamin loss). At the same time, OTR — and more broadly the gas tightness of the entire packaging system, including the seal seams — is also relevant for gas-flushed pouches (MAP – Modified Atmosphere Packaging): after nitrogen flushing, the entire package should keep the protective atmosphere as stable as possible. In principle, gases and volatile substances can also permeate from the inside to the outside (for example nitrogen or aroma compounds), although nitrogen often diffuses significantly more slowly than oxygen.

OTR is commonly measured according to ASTM D3985 (coulometric measurement, “dry”), ASTM F1927, or ISO 15105-2. Stated OTR values are only comparable if the temperature, relative humidity, and test method are identical. Especially in the case of moisture-sensitive barrier materials such as EVOH, relative humidity can have a significant influence on the results.

The following values are normalized OTR ranges for a film of approximately 25 µm at 25°C / 0% RH: