Proteins extrusion

Stojceska et ah (2008) studied the incorporation of cauliflower trimmings into ready-to-eat expanded products (snacks) and their effect on the textural and functional properties of extrudates. It was found that addition of cauliflower significantly increased the dietary fiber and levels of proteins. Extrusion cooking significantly (P < 0.0001) increased the level of phenolic compounds and antioxidants but significantly (P < 0.001) decreased protein in vitro digestibility and fiber content in... 

Extrusion has found wide application in the production of snack foods and breakfast cereals from maize, as well as producing textured soya proteins. Extrusion technology should be investigated as a means of preparing novel textured proteins from animal sources. 

Protein extrusion reactions are effective only when the protein active site constitutes an integral substructure as that which occurs in the iron-sulfur proteins with Fe S core and in heme iron proteins where it is possible to extrude the iron-protoporphyrin IX prosthetic group. 

Plastics and fibers have been produced from regenerated proteins obtained from a number of sources [17]. The process involves dispersing the proteins in dilute sodium hydroxide followed by extrusion through a spinneret into an acid bath to form the fibers that are then crosslinked with formaldehyde to improve strength. The fibers are used along with silk and wool. 

Currently, five different molecular classes of mdr efflux pumps are known [5], While pumps of the the ATP-binding cassette (ABC) transporter superfamily are driven by ATP hydrolysis, the other four superfamilies called resistance-nodulation-division (RND), major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE), and small multidrag resistance transporter (SMR) are driven by the proton-motive force across the cytoplasmic membrane. Usually a single pump protein is located within the cytoplasmic membrane. However, the RND-type pumps which are restricted to Gram-negative bacteria consist of two additional components, a periplasmic membrane fusion protein (MFP) which connects the efflux pump to an outer... 

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. 

We have created structured networks in whey proteins using mild heat and shear, to create reversible TWPs. By understanding on a molecular basis, the effects of shear, ways of creating new functionality can be developed. This will enable development of extrusion parameters that permit controlled denaturation of whey proteins. 

The extrusion process frequently results in realignment of disulfide bonds and breakage of intramolecular bonds. Disulfide bonds stabilize the tertiary structure of protein and may limit protein imfolding during extrusion (Taylor et al., 2006). Flow and melt characteristics were improved when other proteins were extruded with disulfide reducing agents (Areas, 1992), which indicates that disulfide bonds adversely affect... 

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). 

Denaturation and aggregation of whey proteins are affected by the pH of extrusion. When extruding WPI, alkaline conditions increase denaturation and solubility, decrease pasting properties, and produce more pronounced microstructural changes (Onwulata et ah, 2006). Denaturation in the extruder causes whey proteins to form small primary aggregates that combine to form large clusters. The clusters are then aligned by shear to form fibrous structures. 

Structural changes on the whey proteins from the effect of extrusion cooking were examined by scanning electron microscopy and TEM. Changes in the microstructure of WPI (Pig. 5.3) show the transition from... 

TABLE 5.3 Extrusion melt temperatures of whey proteins (Onwulata et ai, 2003a)... 

Extrusion cook temperature Melt (°C) pH Protein (%) Insoluble (%) Digestibility (%)... 

TABLE 5.5 Physical properties of whey protein isolate as function of extrusion temperature (Onwulata et at., 2003a)... 

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