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Developing soy protein isolate-based biopolymers with enzyme in food packaging
E. MOHAMMAD ZADEH (1). (1) Virginia Tech, Blacksburg, VA, U.S.A.

Plant-based biopolymer materials are becoming attractive as an alternative to animal-based biopolymers through recent technical improvement and rising social-cultural and hygienic concerns. Soy protein isolate (SPI) with more than 90% protein purity, was enzymatically modified with transglutaminase and fabricated with glycerol as a plasticizer at three different enzyme incubation times (1h, 2h & 3h) and two protein denaturation temperatures (80 & 90 °C). Tensile strength, percent elongation, and surface hydrophobicity of the films were characterized comparing to a control film which was not treated with the enzyme, and the viscosity of the film forming solution was measured by concentric rheometer as a function of enzymatic incubation time. Enzymatically modified films showed significant increase in mechanical properties and initial contact angle of the films comparing to the control film. Contact angle of the airside of the films were higher than the plateside, which could be attributed to the influence of orientation of molecules during drying and material of the plate. Increasing enzyme incubation time increased tensile strength and reduced percent elongation of films prepared at 80 °C, however, it did not have a significant effect on the films prepared at 90 °C (p>0.05). The viscosity profile of the film forming solution treated with the enzyme was significantly increased as the incubation time increased, which is an excellent evidence of enzymatic treatment to biopolymeric film.  It is in good agreement with mechanical properties of SPI based films. Based on above observations, the enzymatic treatment to protein based polymer  can be a useful way to control the physical properties of protein based biopolymeric film and this treatment can be applied to the wide spectrum of business areas such as  packaging, food, pharmaceutical, and agricultural industries. 

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