Permeation of water vapour, nitrogen, oxygen and carbon dioxide through whey protein isolate based films and coatings-Permselectivity and activation energy

The aim of this study was to evaluate the influence of relative humidity (RH) on the oxygen permeability and water vapour transmission rate (WVTR) of whey protein coated Polyethylene terephthalate (PET) or whey protein monolayer films. Furthermore, the activation energies for the permeability of oxygen, carbon dioxide and nitrogen as well as the permselectivities under different set of temperatures were measured. The results showed that the permeability values through the whey protein coating and whey protein film increased with increasing RH. The water vapour permeability measured at 50% RH of (9.3 +/- 0.6) (10) cm(3) (STP) cm cm(-2) s(-1) Pa-1 increased to (16.2 +/- 0.9) (10) cm(-3) (STP) cm cm(-2) s(-1) Pa-1 at 85% RH. An increase in temperature showed an expected increase of the permeability in both uncoated PET and the whey protein monolayer. The permselectivity of whey protein film was determined and the calculated ratios of the permselectivity (P(N-2)/P(O-2)/P(CO2):1/(4-6/(34-35)) differed from the simplified ratios given in the literature (P(N-2)/P(O-2)/P(CO2):1/4/16). Furthermore the calculated activation energy values for whey (51 kJ mol(-1)) were in agreement with other studies. (C) 2015 Elsevier Ltd. All rights reserved.