Effect of storage temperature and time on stability of poly(lactide)-whey protein isolate laminated films

The stability of biopolymeric multilayer film fabricated from poly(lactide) (PLA) and glycerol-plasticized whey protein isolate (WPI), PLA/WPI/PLA, at 4 degrees C, 25 degrees C, and 35 degrees C were examined. The PLA/WPI/PLA film showed small rates of decreasing in transparency and increasing total color difference. Storage at 35 degrees C caused the film to become stronger and less extendible. The multilayer structures showed lower tensile strength and higher elongation over storage at 4 degrees C and 25 degrees C. Oxygen and water vapor barrier abilities of PLA/WPI/PLA gradually improved over time, especially at 35 degrees C. The changes in properties of laminate structure can be empirically fitted with either zero- or first-order reaction kinetics, with overall R-2 0.90. The results suggested that PLA/WPI/PLA film could be stored at 4-35 degrees C, 50-59% RH, for extended period of inventory time. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43547.