Rheological, Thermal and Microstructural Properties of Whey Protein-Cassava Starch Gels

Mixed gels of cassava starch (CS) and a whey protein isolate (WPI), obtained by heating solutions of 10% total solids, pH 5.75 to 85°C, were characterized as a function of the starch fraction, θ_s, by axial compression, small-amplitude oscillatory rheometry, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Gelation did not occur for θ_s > 0.7. In the range 0<θ_s < 0.4 mixed gels showed higher mechanical (E, elastic modulus) and rheological (G′, storage modulus) properties than pure gels, with maximum values for θ_s= 0.2–0.3. Viscoelastic measurements as a function of time showed that gels containing higher levels of WPI developed a larger G. Blends of both biopolymers showed independent thermal transitions in DSC measurements, related to gelatinization and denaturation. Microstructure of a mixed gel formed at θ_s= 0.2 showed a continuous matrix formed by strands of WPI particle aggregates and an independent CS phase.