Rheological and Thermo-mechanical Characterization of Starch – Protein Mixtures

The knowledge of the properties of model food systems is essential for designing new products with desired functionality. In order to address this issue, the present study was focused on mixtures consisting of 85% potato starch and 15% powdered eggs, gluten or soy protein concentrates. The nature of the proteins used in admixture with starch had a decisive role on the rheological properties of the batters and thermo-mechanical behavior of the doughs. The fundamental rheology tests indicated a solid like behavior with a strong cross-linked network for admixtures of starch with either gluten or soy, while starch - powdered egg batter showed a weak liquid like behavior. Observations made on gelling process highlighted the narrowed gelling temperatures domains for starch when mixed with proteins. Also protein addition determined the occurrence of a second inflection region in G‘curves associated with protein denaturation. The profile of the Mixolab curves varied with the type of protein, indicating low stability of the doughs and rather poor water holding capacity at kneading, especially in case of the powdered egg containing sample. The soy proteins exhibited the highest ability to retain water while heating the doughs. The interference of the protein products with starch granules swelling and gelatinization at thermal treatment depended on their composition, structural properties and thermal stability. The highest stability at 90°C was registered for the sample with soy protein, whereas the gluten containing mixture exhibited the lowest tendency of starch retrogradation.