Extrusion performance and physicochemical characterization of texturized native and chemically modified whey proteins in carbohydrate-containing system

Several approaches to modify the functional characteristics of whey proteins for increased versatility and improved performance during extrusion were investigated. Esterification with n-propanol, acetylation with acetic anhydride and pH modification (5.4 and 8.5) were selected a alternative techniques to modify whey protein isolate (WPI). Modified and native WPI-corn starch blends were extruded at various process conditions of temperature (110-1700C); screw speed (250-450 rpm); moisture content (17-41$spcirc$C); and protein concentration (0-70%). Physicochemical and structural properties of feeds and extrudates were related to the different chemical changes occurring during extrusion. By modifying the reactivity of either the free amino or carboxyl groups of the protein, texturization and/or puffing of corn starch-based WPI-containing products can be controlled. An optimum between the presence of disulfide bonds and hydrophobic interactions to form a properly texturized product from whey protein isolates was observed. Disulfide bonds contributed to the formation of hard, non cohesive products, whereas hydrophobic interactions resulted in brittle, less cohesive extrudates. Free amino groups of whey proteins appeared to play an important role in texture formation. An increase in the negative charge of the protein seemed to favor the texturization of whey proteins.;A great extent of fiber alignment as well as strong protein-carbohydrate interactions were found in 70% alkaline WPI-CS extrudates, suggesting the presence of a texturized structure.;Biopolymerization was another approach to modify the functionality of WPI. Complex formation between whey protein isolates and anionic polysaccharides, such as carboxymethyl cellulose (CMC) and sodium alginate (ALG) via extrusion, was studied by monitoring protein and carbohydrate solubilities in the extrudates. Inclusion of 1% CMC in native, acid and alkaline WPI-CS blends lead to products with a greater extent of texturization.