Texturization, extrusion

Plastics materials may be produced from casein by plasticising with water, extrusion and then cross-linking with formaldehyde (formolisation). The resultant products have a pleasant horn-like texture and are useful for decorative purposes. The amount of casein produced has decreased since World War n but was still one of the preferred materials for use in the decorative button industry until quite recently. 

The properties of mesophase pitch-based carbon fibers can vary significantly with fiber texture. Inspection of the cross-section of a circular mesophase fiber usually shows that the graphitic structure converges toward the center of the fiber. This radial texture develops when flow is fully developed during extrusion through the spinnerette. Endo [48] has shown that this texture of mesophase pitch-based carbon fibers is a direct reflection of their underlying molecular structure. 

Extrusion-cooking is an alternative method (7) for texturization, mixing or cooking which is nowadays currently used by the food industry for the... 

Extrusion Texturized Dairy Proteins Processing and Application... 

The higher protein content whey products are used in many products, and have been mainly promoted for their health benefits. Our contribution is creating extrusion texturized whey products that expands the range of products that can contain whey proteins (Onwulata, 2009 Onwulata et al., 2010). 

There is a continuing interest to improve and extend the fimctional properties range of dairy proteins to provide both health benefits and their characteristic physical behaviors under different temperature, moisture, and pH conditions so that they may be included in foods that ordinarily do not contain them. One such research area is the extrusion texturization of whey proteins, which have resulted in dairy proteins with new characteristics imparted by a controlled texturization process, depending on the application desired (Hale et al., 2002 Manoi and Rizvi, 2008 Onwulata, 2009 Onwulata et al., 1998). Protein texturization is a two-step process that involves, first, the unfolding of the globular structure (denaturation) and, second, the alignments of the partially unfolded structures in the direction of mass flow in the extruder. The surface characteristics are imparted at the extruder die as the molten mass exits (Onwulata et al., 2003a). 

Extrusion texturization is a process that uses mechanical shear, heat, and pressure generated in the food extruder to change the structures of food components, including proteins (Harper, 1986). Protein texturization creates filamentous structures, crumbly surfaces, or other physical formations by restructuring or realigning folded or tightly wound globular structures into stretched, layered, or cross-linked mass (Kinsella and Franzen, 1978). 

Purely thermal denaturation of proteins requires much longer times collagen in moist heat below 120 °C needs 30 min to denature (Meyer et ah, 2005), wheat glutens must be subjected to 200-215 °C of dry heat for 72 min (Friedman et ah, 1987), and as mentioned above, whey proteins require at least 50 °C and 30 min for texturization without the use of extrusion processing. 

Polyacrylamide gel electrophoresis results suggest that p-LG undergoes a greater conformational loss as a fimction of extrusion temperature than a-LA, presumably due to intermolecular disulfide bond formation. Atomic force microscopy indicates that texturization results in a loss of secondary structure of aroimd 15%, total loss of globular structure at 78 °C, and conversion to a random coil at 100 °C (Qi and Onwulata, 2011). Moisture has a small effect on whey protein texturization, whereas temperature has the largest effect. Extrusion at or above 75 °C leads to a uniform densely packed polymeric product with no secondary structural elements (mostly a-helix) remaining (Qi and Onwulata, 2011). 

Extrusion texturization minimizes the water binding capacity of dairy protein products, in decreasing order, WPI > WPC > NDM, as temperature increases, making them interact better with starch. 

Our group has used twin-screw extrusion to produce many texturized whey-fortified puffed snacks. Whey protein has been blended with barley flour, com meal, rice flour, and wheat starch prior to extrusion, leading to corn puffs with a protein content of 20% instead of the usual 2% (Onwulata et al., 2001a). 

Extrusion is an effective means of denaturing whey proteins to create texturized products. TWP may be used as an ingredient to improve the characteristics of many foods. The production of snack foods wifh... 

Extrusion processing texturizes WPCs, WL AC, and WPl, but the greatest amoimt of texturing occurred with WPL... 

Texturized or denatured WPl retained its native protein value, functionality, and digestibility when extruded below 50 °C changes in functionality occur at 65 °C and above. Through careful selection of extrusion conditions of temperature and moisture, TWPs with unique functionality can be produced. The degree of texturization increased with increasing temperature, but temperatures higher than 100 °C may be needed to form fibrous structures with WPl. 

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. 

Cheftel, J. C., Kitagawa, M., and Queguiner, C. (1992). New protein texturization processes by extrusion cooking at high moisture levels. Food Rev. Int. 8, 235-275. 

Hale, A. B., Carpenter, C. E., and Walsh, M. K. (2002). Instrumental and consumer evaluation of beef patties extended with extrusion-textured whey proteins. /. Food Sci. 67,1267-1270. 

Harper, J. M. (1986). Extrusion texturization of foods. Food Technol. 40, 70-76. 

Holay, S. H. and Harper, J. M. (1982). Influence of the extrusion shear environment on plant protein texturization. J. Food Sci. 47,1869-1874. 

Manoi, K. and Rizvi, S. S. H. (2008). Rheological characterizations of texturized whey protein concentrate-based powders produced by reactive supercritical fluid extrusion. Food Res. Int. 41, 786-796. 

Onwulata, C. I. (2009). Use of extrusion-texturized whey protein isolates in puffed corn meal. J. Food Proc. Pres. 34(2010), 571-586. 

Qi, P. X. and Onwulata, C. 1. (2011). Physical properties, molecular structures and protein quality of texturized whey protein isolate (WPl) Effect of extrusion moisture content. /. Dairy Sci. (Accepted for publication). doi 10.3168/jds.2010-3942. 

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