Calorimetric, rheological, and structural properties of potato protein and potato starch composites and gels

Composites of potato protein (PP) to potato starch (PS) weight ratios of 1: 0.5, 1: 1, 1: 3, and 1: 7, and their thermally induced (90 degrees C for 20 min) gels were prepared, and the calorimetric, rheological, and structural properties were investigated. Data of Delta H (heat of phase transition) were close to Delta HPP-PS composite indicating that PP and PS underwent phase transitions independently during thermal treatment of the PP-PS composites. The onset of gelation (T-gel) increased from 57.9 to 61.9 degrees C, and it became hard to identify as the PP content increased, indicating that PS formed a gel more easily than PP. The decrease of the degree of dependence of G' on frequency sweep (z') from 0.20 to 0.08 with the increase of the strength of molecular interactions (K) from 1.49 to 2.22 indicated that the physical interactions in PP-PS gels decreased but the covalent interactions and the strengths of the gels increased as the PP content increased. Potato starch prevented the thermally induced secondary structural changes of PP, and a more uniform network structure was formed in the PP-PS gels as the PS content increased. Thus, by adjusting the ratios of PP and PS, the quality of PP-PS gels could be enhanced.