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Improve quality of casein film with wax.

Edible films are environmentally friendly and have the potential to reduce waste. However, many of the films are not too flexible, and are unable to withstand the mechanical stresses they experience in food packaging applications. Previous research has shown that protein film supplemented with zein hydrolysate (ZH) increased in terms of its flexibility but failed to reduce its water vapor permeability (WVP).

The objective of research at Tuskegee University was to determine the impact of ZH, transglutaminase (TG) and wax emulsion on the WVP, strength and elasticity of casein-based film. Scientists found that a wax coating can decrease the WVP, and ZH can increase the flexibility of edible film fabricated from casein.

Scientists undertook a 3 x 3 factorial design with three film formulations that were crossed with three wax treatments. Formulation I (F-I) was only composed of casein. Formulation II (F-II) included casein, ZH and inactivated TG. Formulation III (F-III) included casein, ZH and active TG.

The three wax treatments included a formulation (W-I) which did not have wax. Wax II (W-II) was a film coated with a wax emulsion. Wax III (W-III) was a wax emulsion mixed with a film formulation. Researchers added the TG into the film formulations to cross-link the proteins.

Including wax in the formulations significantly decreased the WVP of the film. The WVP of films coated with wax or mixed with wax decreased by 88% and 18%, respectively, compared to the control, which had no wax. Adding TG did not have any significant effect on the WVP of the film. The protein molecules in the film were cross-linked by TG. TG did not have any significant impact on the performance of the film. Adding ZH to the film reduced the film's tensile strength and Young's modulus by approximately 17% and 42%, and increased the flexibility of the film by 31%.

Further information. Mohammed Biswas, Department of Chemistry, Tuskegee University, 303 Armstrong Hall, Tuskegee, AL 36088; phone: 334-724-4491; email:
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Publication:Emerging Food R&D Report
Date:Mar 1, 2006
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