Protein materials main plasticizers

However, one of the main drawbacks of these protein materials is their high sensitivity to water. As interaction of a protein film with water is a sum of complex phenomena, different parameters can be taken into account. The water vapor barrier properties and the plasticizing effect of water in the film (with its important influence on mechanical properties) belong to the most studied characteristics, probably because they can easily be linked to macroscopic measurements. 

Until recently, research work on the structure, properties and applications of proteins were mainly considered within the scientific field of Food Science. To reach a better understanding of properties and to define the potential applications of material proteins, it is essential to compare their structural features with those of chemically synthesised organic polymers used to produce plastic materials. Novel research on nonfood uses of agricultural resources, and especially on material proteins , has led to the application of Polymer Science concepts and tools to investigate the structure-function relationships of these macromolecular organisations. This involves ... 

Table 11.5 MW and main sub-units of protein-materials used to form bioplastics and comparison with some conventional synthetic plastics...

Guilbert, S. (2002) Protein-based Bio-Plastics formulation, thermoplastic processing and main applications International Congress Trade Show The Industrial Applications of Bioplastics, 3rd, 4th and 5th February Gunatillake P.A. and Adhikari R. (2003) Biodegradable synthetic polymers for tissue engineering , European Cells and Materials, 5, 1-16. 

Among the different categories of biodegradable plastics obtained from agropolymers, both starch/polyesters blends and microbial biodegradable plastics satisfied the majority of requirements asked by the plastic packaging industries (material qualities, processability, performances, etc.). Other bioplastics based on natural polysaccharides or proteins are mainly interesting for their low cost but their non-reproduetive quality and lower performances are still a handicap. 

Biodegradable films made from edible biopolymers from renewable sources could become an important factor in reducing the environmental impact of plastic waste. Proteins, lipids, and polysaccharides are the main biopolymers employed to make edible films and coatings. Which of these components are present in different proportions and determine the properties of the material, as a barrier to water vapor, oxygen, carbon dioxide, and lipid transfer in food systems (Gomez-Guillen et al. 2002 and 2009). 

Macro-coating is used mainly to stabilise fragrances or transform them from liquid to free-flowing solid powder. Microencapsulation or nanoencapsulation is the process of enclosing a substance inside a miniature capsule. These capsules are referred to as microcapsules or nanocapsules. The substance inside the capsule can be a gas, liquid or solid. The capsule wall can consist of various materials, such a wax, plastic or biopolymers like proteins or polysaccharides. 

Food polymers and the behaviour of their mixtures are mainly responsible for the structure-properties relationship in both food and chyme. The two basic features of food are that its biopolymers, proteins and polysaccharides are its main construction materials and water is the main medium, solvent and plasticizer. In other words, three components— protein, polysaccharide and water—are the main elements of food structure that are principally responsible for quality of foods (see also Chapter 13). 

Moisture, no doubt, is an effective plasticizer. However, its exact effect on the mechanical properties of cellular solid foods, with the possible exception of the class of soluble low molecular materials (see below), cannot be predicted on the basis of their Tg even if there were an acceptable way to determine it. This is primarily because whenever the cell wall solid is mainly made of a high molecular weight polymer, such as starch and/or protein, moisture can affect its various mechanical properties differently and in a manner that must be determined experimentally. 

X-ray diffraction (XRD) is a nondestructive technique that operates on the nanometre scale based on the elastic scattering of X-rays from structures that have long range order (i.e. an organised structure of some sort, e.g. periodicity, such as in a crystal or polymer). It can be used to identify and characterise a diverse range of materials, such as metals, minerals, polymers, catalysts, plastics, pharmaceuticals, proteins, thin-lihn coatings, ceramics and semiconductors. The two main types of XRD are X-ray crystallography and X-ray powder diffraction. 

Substances of organic origin, such as wood flour, used for consumption products and in the production of electrical insulation cellulosic fibers (textiles, paper fibers and particles) used mainly to increase impact resistance fruit shell flour, which increases the fluidity of plastic materials under pressing and enhances the dielectric properties and appearance of final products protein flour—casein and soya flours for example—used with carbamides. 

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