Plasticizer effect on oxygen permeability of beta-lactoglobulin films.

Plasticizer effect on oxygen permeability (OP) of beta-lactoglobulin (beta-Lg) films was studied. Propylene glycol (PG), glycerol (Gly), sorbitol (Sor), sucrose (Suc), and polyethylene glycol at MW 200 and 400 (PEG 200 and PEG 400, respectively) were studied due to their differences in composition, shape, and size. Suc-plasticized beta-Lg films gave the best oxygen barrier (OP < 0.05 cm3 x microm/m2 x day x kPa). Gly- and PG-plasticized films had similar OP values, and both had higher OP than Sor-plasticized films. PEG 200- and PEG 400-plasticized films were the poorest oxygen barriers. Empirical equations including plasticizer efficiencies for OP were employed to elucidate the relationships between OP of plasticized beta-Lg films and plasticizer type and content. Plasticizer efficiency ratios between mechanical and OP properties of beta-Lg films show the relative efficiency of plasticizers in modifying mechanical and OP properties. A large ratio is desirable.