Combination of radio frequency heating and antibacterial agents for microorganism control in the production of packaged tofu

The microorganism control in packaged tofu by radio frequency (RF) heating combined with antimicrobial agents was investigated. The inactivation of vegetative cells and spores by RF heating alone or in combination with antimicrobial agents was evaluated. Results showed that vegetative cells of typical food microorganisms, such as E. coli, S. aureus, and Bacillus subtilis, were completely inactivated by RF heating at 80 °C for 20 min, while no significant reduction in the population of spores was observed. Additionally, the growth of Bacillus spores was effectively inhibited by 0.312 mg/g of nisin. The total viable count (TVC) in RF-treated packaged tofu was below 2 log CFU/g during the storage at 4 or 37 °C for 10 days in the presence of nisin. Furthermore, the quality analysis indicated that the pH, texture, color, and volatile profile of samples were well maintained, which contributed to the favorable sensory acceptance of the consumers. These results suggested that effective microorganism control in packaged tofu was achieved by combining RF heating and nisin. The developed method was recommended to prevent spoilage of packaged tofu and extend its shelf-life.