Effect of temperature and power frequency on milk fouling in an ohmic heater

Ohmic heating has an advantage over conventional indirect heating methods because heater (electrode) surfaces temperatures are comparatively lower as heat is generated within bulk fluid. However, it is difficult to sustain this advantage over time. As soon as fouling takes place, electrode temperature starts rising and eventually it becomes higher than bulk fluid temperature. In this study, we have analysed the changing temperature profile and its impact on the fouling process during thermal processing of milk in a cylindrical ohmic heater. Furthermore, the impact of power supply frequency on the corrosion of electrode surfaces and in turn on fouling has also been investigated. The use of a 10 kHz power supply is observed to reduce corrosion and result in less fouling compared with a 50 Hz mains power supply.