Properties of konjac glucomannan–whey protein isolate blend films

Edible composite packaging has been developed by blending biocomponents for specific applications, aiming to take advantage of complementary functional properties or to overcome their respective flaws. The aim of this work was to study the effect of incorporation of whey protein isolate (WPI) on the properties of konjac glucomannan (KGM) based films. Five aqueous solutions of KGM and/or WPI were prepared by casting and solvent evaporation of 1:0, 0.8:3.4, 0.6:3.6, 0.4:3.8 and 0:4.2 g KGM:g WPI/100 g solution. Glycerol (Gly) was used as a plasticizer at 1.5 and 1.8 g/100 g solution. The result showed that incorporated WPI proportionally increased transparency of KGM-based films. An increase in proportion of WPI resulted in decreased tensile strength and elastic modulus as well as improved flexibility. The incorporation of WPI into the KGM matrix led to an increase in water insolubility which enhanced product integrity and water resistance. Nevertheless, WPI did not improve water vapor barrier of KGM–WPI films. WPI and blend film with the highest concentration of WPI could be heat sealed at 175 °C. Overall, the range of Gly in this study did not apparently affect properties of the films.     

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 °C, 25 °C, and 35 °C were examined. The PLA/WPI/PLA film showed small rates of decreasing in transparency and increasing total color difference. Storage at 35 °C caused the film to become stronger and less extendible. The multilayer structures showed lower tensile strength and higher elongation over storage at 4 °C and 25 °C. Oxygen and water vapor barrier abilities of PLA/WPI/PLA gradually improved over time, especially at 35 °C. The changes in properties of laminate structure can be empirically fitted with either zero‐ or first‐order reaction kinetics, with overall R² ≥ 0.90. The results suggested that PLA/WPI/PLA film could be stored at 4–35 °C, 50–59% RH, for extended period of inventory time. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43547.