Performance comparison between the free running oscillator and 50 Ω radio frequency systems

•Performance of free running oscillator and 50 Ω RF systems was compared.•Free running oscillator system had faster heating rates and higher energy efficiency.•50 Ω RF system had better power control accuracy, heating uniformity and stability.•Comparison results may promote practical applications of two RF systems.

Two common kinds of radio frequency (RF) systems (free running oscillator and 50 Ω) are widely applied in industry and research. However, their unclear performances based on different operational mechanisms influence effective implementations of the two systems. The purpose of this research was to explore advantages and disadvantages of the two systems by experimental comparison. The results showed that heating rates and energy efficiency of the free running oscillator RF system were higher than those of the 50 Ω RF system under the same conditions (e.g. powers, electrode gaps, sample sizes and moisture contents), but control accuracy of the 50 Ω RF system was better than that of the free running oscillator RF system since its RF power could be adjusted under the same electrode gap. The RF heating uniformity and stability of the 50 Ω RF system were also better than those of the free running oscillator RF system. These comparison results may provide detailed performance information of the two RF systems and help to promote further practical applications of the two RF systems in food processing industry.