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Title: Effect of type and content of modified montmorillonite on the structure and properties of bio-nanocomposite films based on soy protein isolate and montmorillonite

Author
item KUMAR, PRABHAT - North Carolina State University
item SANDEEP, KANDIYAN - North Carolina State University
item ALAWI, SAJID - Kennesaw State University
item Truong, Van Den
item GORGA, RUSSELL - North Carolina State University

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2010
Publication Date: 7/1/2010
Citation: Kumar, P., Sandeep, K.P., Alawi, S., Truong, V., Gorga, R.E. 2010. Effect of type and content of modified montmorillonite on the structure and properties of bio-nanocomposite films based on soy protein isolate and montmorillonite. Journal of Food Science. 75(5):N46-N56.

Interpretive Summary: The non-degradable and non-renewable nature of plastic packaging has led to a renewed interest in packaging materials based on biopolymers such as proteins, starch, cellulose and other polysaccharides derived from renewable sources. Commercialization of biopolymer-based packaging materials has been implemented and this development can solve the waste disposal problem to a certain extent. However, biopolymers do not have the mechanical and barrier properties matching those of plastics. Recently, a new class of materials represented by bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates, Cloisite 20A and Cloisite 30B) has proven to be a promising option in improving the properties of these biopolymer-based packaging materials. Therefore, efforts have been geared towards developing bio-nanocomposites for food packaging films with improved mechanical, barrier, rheological, and thermal properties. This study demonstrated that bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) with improved properties can be prepared using melt extrusion. Bio-nanocomposite films with 10% Cloisite 30B had mechanical properties comparable to those of LDPE and PVDC plastic films which are currently used in various food packaging applications. However, much higher water vapor permeability of these films as compared to those of LDPE and PVDC might limit the applications of these bio-nanocomposite films to packaging of high moisture foods such as fresh fruits and vegetables.

Technical Abstract: The non-biodegradable and non-renewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. Effect of different types (Cloisite 20A and Cloisite 30B) and contents (0-15%) of modified MMT on the structure and properties of SPI-MMT nanocomposite films were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used for structural characterization of the films. Properties of the films determined included color, mechanical and dynamic mechanical properties, thermal stability, and water vapor permeability (WVP). The arrangement of MMT in the bio-nanocomposite matrix ranged from exfoliated to intercalated depending on the type and content of modified MMT. At a MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical, dynamic mechanical, and water barrier properties as compared to those based on natural MMT (Cloisite Na+). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics which are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the applications of these films to packaging of high moisture foods such as fresh fruits and vegetables.