Whey is a by-product of cheese-making and casein manufacture in dairy industries. It is considered as one of the most polluting by-product in environment. Otherwise, whey is an excellent source of functional proteins that can be used in food industry for example dairy foods, bakery products, infant foods and beverages. Therefore to extend using of this protein improving the performance characteristics of whey proteins in food products is necessary. Thermal treatment and pH adjustment are factors that influence functional properties of whey proteins. In this research, the effect of pH adjustment and thermal treatment at different temperature on conformation structure of whey proteins were studied. These treatments led to creation of different aggregate sizes. A Response Surface design (RSM) was used to investigate the effect of pH, temperature and thermal treatment on of aggregate sizes, WPC dispersion turbidity over time, hydrophobicity and insoluble aggregates after freeze drying. These treatments led to creation of aggregates with different sizes. After heat treatment and decrease of the pH to pH~4, size of aggregates, turbidity of WPC dispersions, amount of insoluble aggregates and hydrophobicity of aggregates after freeze drying, was increased. At pH 7, as the temperature of thermal process increased the size of aggregates increased too (without heat treatment), but in heat treated samples from pH 4-9, as the temperature of thermal process increased the size of aggregates increased. In the next step, whey protein aggregate was used as an emulsifier for oil in water emulsion at different pH. Result showed that increase in size of aggregates and decrease in emulsion pH led to increase the firmness of emulsion, size of emulsion droplet and viscosity and decrease creaming. Keywords: whey protein, Nano, Thermal treatment, pH, Emulsion, Size of droplet, Turbidity, Viscosity.
