Influence and comparison of thermal, ultrasonic and thermo-sonic treatments on microbiological quality and sensory properties of rennet cheese whey

Ultrasonication and thermo-sonication belong to alternative, non-thermal food processing methods. The aim of this study was to investigate the influence of different ultrasound power inputs (240 W, 320 W, 400 W) without and in combination with heat pre-treatment on microbial inactivation and sensory properties of rennet cheese whey in comparison with conventional pasteurization batch processes. Ultrasonication treatments had no impact on reduction of any group of studied microorganisms. Microbial inactivation caused by thermo-sonication treatments with pre-heating to 35 °C or 45 °C increased with nominal power input and/or exposure times and was probably due to the heat improved ultrasonic cavitation. Thermo-sonication treatments at nominal power input (400 W) and preheating to 55 °C were the most effective resulting in greater microbial reduction compared to that observed by simulating pasteurization processes, but occurred probably due to developed heat solely. Sensory properties after ultrasonication and thermo-sonication were considerably improved in comparison with that after simulated pasteurization processes. Mouth feel of whey samples was considerably better, there was no occurrence of sediment and colour remained unchanged in almost all samples.