Films whey proteins

It is demonstrated here that extrusion is an effective tool for texturing whey proteins to create new functions for dairy proteins and that thermally denatured WPl is a unique ingredient that can be used in large amounts in nontraditional applications for non-TWPl. This review covers the use of extrusion texturized dairy ingredients in foods however, there are other examples of fhe successful use of this technique along with the product, TWPl in different types of nonfood applications, such as in biodegradable films, and bioplastics. 

The applications of colloid solutions are not restricted to paints and clay. They are also to be found in inks, mineral suspensions, pulp and paper making, pharmaceuticals, cosmetic preparations, photographic films, foams, soaps, micelles, polymer solutions and in many biological systems, for example within the cell. Many food products can be considered colloidal systems. For example, milk is an interesting mixture containing over 100 proteins, mainly large casein and whey proteins [6,7]. 

Whey protein films similar properties to casein films, but water insoluble eating required... 

McHugh and Krochta (Gennadios et al. 1994) observed that composite films based on fatty alcohols/whey proteins were less effective as moisture barriers than fatty acids/whey proteins. This discrepancy with Kester and Fennema s study can be... 

Kim, S.J., and Ustunol, Z. (2001). Sensory attributes of whey protein isolate and candelilla wax emulsion edible films. J. FoodSci. 66, 901-911. 

McHugh, T.H., and Krochta, J.M. (1994a). Water-vapor permeability properties of edible whey protein-lipid emulsion films. J. American Oil Chem. Soc. 71, 307-312. 

In native state, proteins exist as either fibrous or globular form. Protein should be denatured and unfolded to produce an extended chain structure to form film. Extended protein chains can interact through hydrogen, ionic, and hydrophobic bonds to form a three-dimensional stmcture (24). Protein films are excellent gas barriers but poor moisture barriers because of their hydrophilic nature. Mechanical properties and gas permeability depend on the relative humidity (1). Al-ameri (25) smdied the antioxidant and mechanical properties of soy, whey and wheat protein, and carrageenan and carboxymethyl cellulose films with incorporated tertiary-butylhy-droquinone (TBHQ), butylated hydroxytoluene (BHT), fenugreek, and rosemary extracts. Armitage et al. (26) studied egg albumin film as a carrier of natural antioxidants to reduce lipid oxidation in cooked and uncooked poultry. 

Interactions between proteins and polysaccharides give rise to various textures in food. Protein-stabilized emulsions can be made more stable by the addition of a polysaccharide. A complex of whey protein isolate and carboxymethylcellulose was found to possess superior emulsifying properties compared to those of the protein alone (Girard et al., 2002). The structure of emulsion interfaces formed by complexes of proteins and carbohydrates can be manipulated by the conditions of the preparation. The sequence of the addition of the biopolymers can alter the interfacial composition of emulsions. The ability to alter interfacial structure of emulsions is a lever which can be used to tailor the delivery of food components and nutrients (Dickinson, 2008). Polysaccharides can be used to control protein adsorption at an air-water interface (Ganzevles et al., 2006). The interface of simultaneously adsorbed films (from mixtures of proteins and polysaccharides) and sequentially adsorbed films (where the protein layer is adsorbed prior to addition of the polysaccharide) are different. The presence of the polysaccharide at the start of the adsorption process hinders the formation of a dense primary interfacial layer (Ganzelves et al., 2008). These observations demonstrate how the order of addition of components can influence interfacial structure. This has implications for foaming and emulsifying applications. 

Perez-Gago, M.B. and Krochta, J.M., Denaturation time and temperature effects on solubility, tensile properties, and oxygen permeability of whey protein films, J. Food Sci., 66, 705, 2001. 

Comparison of the competitive displacement of spread films of whey protein isolate (WPI) and (3-lactoglobulin from an air-water interface with the nonionic surfactant (polyoxyethylene sorbitan monolaurate) Tween 20. Note that the WPI network remains intact at surface pressures (tt) above those at which the (3-lactoglobulm network has failed. The image sizes are indicated in brackets below the images. 

When particles interact through relatively permanent bonds, the displacement induced by compression leads to wrinkles that line up perpendicular to the direction of compression. This feature has been observed experimentally, for example, for proteins found in limg surfactants (Lipp et al., 1998), and the various desorption mechanisms induced by compression have been identified, for example, in 2-hydroxytetracosanoic acid monolayers (Ybert et al., 2002). Furthermore, we believe that the same type of behavior might also be found for adsorbed milk proteins, especially heat-treated whey proteins. The expansion of films formed by particles that crosslink through transient bonds leads to fracture of the films, a mechanism also seen with globular milk proteins (Hotrum et al., 2003). 

While foaming is favored by increased viscosity, hydrophobicity, and solubility, the increase of net charge density caused by succinylation tends to decrease foam stability (FS), since it prevents optimum protein-protein interactions required in a continuous film around air bubbles. Therefore a number of succinylated proteins showed a drop of the FS with increasing degree of modification. This was reported for protein preparations from faba beans [86], peas [72], cottonseed [69], oat [66], and cheese whey protein concentrate [88] for instance. The unfavorable charge effect of succinylation can be overcome by foaming at sufficiently high protein concentration, as shown for faba bean protein isolates [86] and napin from rapeseed [84]. 

Films of whey proteins (formed by thermally induced disulfide cross-linking) are flavorless, transparent to translucent depending on the protein source,excellent gas barri-ers, " and possess good tensile strengths similar to synthetic films. 

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