Extrusion cooking analysis of corn starch and WPI mixture as a model system on the microstructure and thermodynamic parameters

ABSTRACT The objective of this research was to study the impact of extrusion cooking on the microstructure of corn starch and whey protein isolate mixtures, to know the changes in the physicochemical properties of these macromolecules. Three samples were prepared at a concentration of 100/0, 50/50, and 0/100 WPI-Starch (w/w), respectively. Extrusion was carried out in a single-screw extruder. Extrusion caused a significant loss of crystalline structure, as measured by X-ray diffractometry, and 100% gelatinization in all cases, as seen by DSC. At the same time, Raman and FTIR showed a decrease in the intensity of the peaks without the presence of newly formed functional groups; in addition, there was a decrease in viscosity from 2.30 to 0.10 Pa.s. CLSM clearly shows no direct interaction between components, while SEM also confirms the results of DSC and XRD, showing the gelatinization of the starch granule and protein denaturation. Therefore, it is concluded that extrusion under the conditions studied causes a significant change in the chemical structure of extruded products, resulting in a more amorphous and gelatinized system, properties that should be considered when planning produce less caloric snacks reinforced with protein, allowing food developers to fine-tune formulations to meet their customers' needs.