Abstract: As a representative of liquid foods, tomato juice was heated by 2450-MHz microwave. Effect of microwave power on heating rate on tomato juice sample was intestigated, as well as sterilization effects of different microwave powers and time and concentrations of sucrose and NaCl in the sample, and the physicochemical indexes of the tomato juice sterilized by different heating methods were determined. It was found that thermal effect is the most important cause of microwave sterilization. The sterilization effect of microwave heating is greatly impacted by the addition of sucrose and NaCl in the sample. More microbes survive in the tomato juice which contains sucrose and NaCl. After microwave heating, the L value of the tomato juice increases notably while the a value decreases. Compared with traditional heating method, the microwave heating method can retain contents lycopene and vitamin C better.

Key words: tomato juice, microwave heating, sterilization, lycopene