Rheological properties of gelatin/starch composite gels
Rheological properties of gelatin, gelatin/regular and gelatin/waxy corn starch composite gels were investigated using oscillatory shear, constant rate uniaxial and dynamic compression methods to study the similarities between the moduli to interpret the protein-polysaccharide interactions within each system. Composite gelatin/starch gels were tested at a 5% (w/w) gelatin concentration and 0, 1, 3 and 5% (w/w) starch concentration. Scanning electron microscopy, volume fraction and particle sizing experiments further support the results of the rheological tests and help define the protein-polysaccharide interactions. In gelatin/regular starch composite gels, 'G'' and 'E' increased linearly, thus the rigidity of the gels increased with increased volume fraction as a result of the synergistic effect of a secondary amylose gel. This indicated that regular corn starch behaved as an active filler particle. The results for 'G' ' and 'E', for gelatin/waxy starch composite gels, demonstrated a minimal change in rigidity over the concentration range of the waxy corn starch since little response was observed from either test method. Both rheological tests generated similar conclusions about the structure of gelatin/regular and gelatin/waxy corn starch composite gels.