Antiplasticisation and oxygen permeability of starch¯sorbitol films

The thermomechanical properties and oxygen permeability of sorbitol¯starch¯water films were studied. Sorbitol had an antiplasticisation effect for contents below 21% (wt%), as indicated by a ten-fold drop in oxygen permeability 1.43×10-16 cm3 cm/cm2 s Pa for the sample not containing sorbitol and 0.15×10-16 cm3 cm/cm2 s Pa for the sample containing 8.8% of sorbitol. This behaviour was related to changes in secondary relaxations. The motions involved in these relaxations were reduced because of the connections established between starch and sorbitol, leading to decreased diffusion of oxygen molecules. For sorbitol contents above 21% (wt%), oxygen permeability increased slightly. Water produced a classic plasticising effect (an increase of oxygen permeability), but at low sorbitol content (8.8%) this was only moderate due to the effect of sorbitol itself (4.3×10-16 cm3 cm/cm2 s Pa for 23.8% of water).