Stractural and Morphological Characteristics of Whey Protein Concentrate-Modified Starch Complex: Effect of pH and Bioplymers Ratio

In this study, interaction between WPC and OSAS as a function of pH (3, 4, 5 and 6) and biopolymers ratio (1:2, 1:1 and 2:1) at total concentration of 1% w/w was investigated by measuring the structural (turbidity, particles size, Zeta potential, viscometery, FTIR) and morphological (SEM) properties. Maximum zeta potential was observed at 2:1 biopolymers ratio and pH=3. With increasing pH and decreasing ratio of WPC:OSAS, zeta potential value decreased. At ratio 1:2 and pH 6 minimum zeta potential was gained. Minimum particles size was observed at ratio 1:2 and pH=6 (0.819 µm) in which with decreasing pH to 4 and increasing ratio up to 2:1, it was maximized (2.260). Turbidity results was in accordance with particles size measurements and maximum and minimum results was observed at the same points. At ratio 1:2 and pH=4, maximum viscosity was observed (1.301 mPa.s). Reducing the ratio and increasing pH led to minimum viscosity at pH=6 and ratio 2:1 (1.147 mPa.s). In all measured characters, there was significant difference between control (WPC) and complex samples. FTIR study revealed that by complexation between WPC and OSAS, amid II peak was weakened and carboxylated and OSA group's peak were removed. SEM images showed that with formation of electrostatic complex, spherical structures of WPC and OSAS was changed to porous network and sheet structures.