No abstract

Surface response modeling was used to characterize the effect of extrusion processing on the functional properties of corn fiber/corn starch formulations. Process parameters evaluated included screw speed (ZOO-500 rpm), temperature (90-150°C) and pH (3-11). Generally, the water holding capacity of starch increased with increasing extrusion temperature while the water holding capacity of the fiber decreased with increasing extrusion temperature. The foam stability decreased, while the residual moisture increased, with an increase in fiber concentration. X-ray diffraction profiles indicated that extrusion did not affect fiber crystallinity. No significant changes in the ratio of soluble to insoluble fiber were found as a result of extrusion.

Effect of succinylation, acetylation, and reductive alkylation on substructural properties of three milk protein systems (casein, BSA, and whey proteins) was studied. Three levels of modifications were achieved in each case, and changes in the proteins' spectral properties were determined. Casein attained the highest degree of modification for all of the treatments used. Acylation enhanced denaturation and improved surface hydrophobicity of all of the proteins. Modification of BSA resulted in a red-shifted emission fluorescence peaks; however, its circular dichroic (CD) patterns showed insignificant difference from those of the native. This may imply that acylation has affected only the tertiary structure of BSA. Fluorescence and CD profiles of whey proteins and caseins showed considerable changes in their conformational makeup. It appears that acylation may have a more drastic effect on multicomponent proteins, possibly by means of perturbing their protein-protein mode of interaction.

The 7S and 11S fractions of soy protein were isolated from soy flour and recombined with soy protein concentrate at various levels to modify their ratio in different formulations. the role of each fraction on the extrusion performance and texturization behavior of soy proteins was evaluated using twin‐screw extrusion. Both 11S and 7S fractions were found to have significant influence on the degree of texturization of soy protein. In particular, the 11S protein appeared to favor expansion and water holding capacity of the finished product, while an 11S/7S ratio of 1.5 in the feed formulation resulted in a product with the best textural characteristics under the selected extrusion conditions investigated.