Rheology, microstructure and phase behavior of potato starch-protein fibril mixed gel

Effects of adding whey protein fibrils to gels of potato starch with 8 % solids content were determined by rheology, microscopy, and calorimetry. Adding fibrils to starch at 50 % content (w/w) increased starch gelatinization temperature by 1.5 degrees C but decreased associated enthalpy. Fibril addition consistently reduced gel viscosity. Storage modulus (G') of gels increased with fibril content when prepared at pH3.5 but not at pH6.8. Fibrils were dispersed within imaged gels at pH3.5 for contents below 50 %, while separated phases were observed within pH3.5 gels for 50 % fibril content and within pH6.8 gels for all fibril contents. Dilution of gels led to sedimentation of predominantly starch, and both starch and protein content of sediment increased with overall fibril content. Results indicated that associative interactions between fibrils and starch contributed to synergistic increases in gel elasticity at low pH but not at neutral pH conditions under which starch and protein were poorly compatible.