Application of ultrasound in food processing presents novel non-thermal method, with low energy consumption and short treatment time as compared to traditional technological processes. Treatment with this procedure takes few minutes and presents novel method for food processing that can be used for new product development as improvement of technological process what is the purpose of this thesis. The main aim of this thesis was to investigate in what way various ultrasound treatments, with usage of different ultrasound frequencies, power and treatment time, affects functional and physical properties of whey proteins and model systems prepared with whey proteins and diverse supplements like guar gum, methyl cellulose, sucrose and milk powder. The examinations were conducted on powdered whey protein isolates, concentrates, hydrolysates and α- lactalbumin samples. Ultrasound probes of 20 kHz and 30 kHz frequency were used, as well as ultrasound baths of 40 kHz and 500 kHz frequency. Treatment times with ultrasound of 20 kHz, 40 kHz and 500 kHz were 15 and 30 minutes, and with 30 kHz probe 3, 5 and 10 minutes. Investigated whey protein and model system properties were: solubility, foaming and emulsifying properties, pH, conductivity and temperature changes after treatments. Than, the effect of ultrasound on particle size, protein molecular weight using gel electrophoresis, and changes in viscosity and thermophysical properties of suspensions have been investigated. The obtained results showed that ultrasound treatments have different influence on physical and functional properties of investigated systems. Ultrasound treatment with 20 kHz and 40 kHz frequencies caused significant reduction in particle size, and narrowed their distribution, except for whey protein hydrolysates. The same treatment caused improvement in foam capacity and stability, and also increases emulsion activity indexes. Addition of methyl cellulose, guar gum, sucrose and milk powder in combination with ultrasound treatment with 30 kHz showed different influence on investigated properties.