Insight into the inactivation of Bacillus cereus spores by ohmic heating and application in liquid food

Bacillus cereus spores pose a potential threat to various food products, including meat, grain, vegetables, and dairy products, due to their remarkable resistance to environmental stress. Ohmic heating (OH) is an emerging alternative technology for inactivating spores. This study aimed to investigate the effects of OH on B. cereus spores, specifically examining its impact on heat resistance, leakage of intracellular substances, integrity of the cortex and membrane, and structural changes, in order to elucidate the potential inactivation mechanism of OH. The results demonstrated the efficacy of OH in inactivating B. cereus spores in various liquid food products while maintaining product quality. The wet heat resistance of spores decreased after OH treatments at low-temperatures (60–70 ℃), potentially promoting subsequent inactivation. Conversely, resistance increased following OH treatments at higher temperatures and oil bath heating (OB) treatments. Similar inactivation effects were observed between OB and OH when the temperature reached 80 and 98 ℃. Both OH and OB treatments damaged spore structures, resulting in leakage of intracellular substances and disruption of homeostasis. However, OH treatment at 10 V/cm and 50 Hz resulted in less leakage of dipicolinic acid, protein, nucleic acids within the spores, and appeared to have additional effects on the structures within the inner membrane. These findings could facilitate the development of OH as a promising technology for effective spore control in food.