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- Measurement of oxygen transmission rate through foamed materials for bottle closuresPublication . Poças, Maria F.; Ferreira, Belmiro; Pereira, Joel; Hogg, TimThe determination of the oxygen transmission rate (OTR) through closures in glass bottles is becoming increasingly important for quality control of different batches and for development purposes. The Mocon method for measuring OTR is globally accepted and used in different applications. However, one of the major drawbacks this method presents when applied to bottle/closures systems is the long time required to obtain stable measurements when 40 mm long closures are tested. This paper describes a method to obtain OTR values with samples of reduced thickness with much shorter measurements time, since the condition of steady state during measurements is achieved faster and compares the estimated full-length commercial closure OTR with experimental values
- Modelling migration from paper into a food simulantPublication . Poças, Maria de Fátima; Oliveira, Jorge C.; Pereira, Joel R.; Brandsch, Rainer; Hogg, TimThe migration of components from paper into Tenax (R) was studied to determine the influence of molecular size and chemical character of the migrant and the influence of paper characteristics in the migration process The Weibull model was applied because Fick s 2nd law of diffusion gave poor fits in some cases The migration pattern depended on the migrants molecular size and was independent of temperature in the studied range The migration rate decreased with the migrant molecular size The influence of the migrants character (polarity and vapour pressure) on the migration behaviour was also studied nonpolar migrants with high vapour pressure presented low relative migration values and polar migrants presented high values of relative migration Results indicated that the apparent partition coefficient between paper and the simulant Tenax (R) increased with the migrant vapour pressure and with both the paper grammage and the recycled pulp content