Abstract A 27.12 MHz thermostatic radio frequency (RF) system was employed to inactivate Cronobacter sakazakii in powdered infant formula milk. A proportional-integral-derivative controller achieved constant material temperature during the holding period. Hot air and similar dielectric material assistance were used to improve RF heating uniformity. The results showed that the microbial thermal resistance was reduced by increasing temperature (55–70 °C) and water activity (0.2–0.4 at 25 °C). Combined RF and hot air pasteurization (RF-HA) was more effective than single RF and material assistance due to better temperature uniformity. D70°C-value (23.3 min) of Cronobacter sakazakii at water activity of 0.2 from RF-HA was not significantly (P > 0.05) higher than that under hot water treatment (20.8 min), indicating that thermal effect led to microbial inactivation. Flow cytometry and transmission electron microscopy further confirmed that RF had no additional damage to cell membrane. The findings contribute to better understanding of RF pasteurization mechanism.

中文翻译：

---

使用恒温射频热灭活婴儿配方奶粉中的坂崎克罗诺杆菌 ATCC 29544

摘要 采用 27.12 MHz 恒温射频 (RF) 系统灭活婴儿配方奶粉中的坂崎克罗诺杆菌。比例积分微分控制器在保温期间实现了恒定的材料温度。热空气和类似的介电材料辅助用于改善射频加热均匀性。结果表明，微生物热阻随着温度（55-70°C）和水分活度（25°C时为0.2-0.4）的升高而降低。由于更好的温度均匀性，组合 RF 和热空气巴氏杀菌 (RF-HA) 比单一 RF 和材料辅助更有效。来自RF-HA的水分活度为0.2的坂崎克罗诺杆菌的D70°C值（23.3分钟）与热水处理（20.8分钟）相比没有显着（P> 0.05）高，表明热效应导致微生物失活。流式细胞术和透射电镜进一步证实RF对细胞膜没有额外的损伤。这些发现有助于更好地了解射频巴氏杀菌机制。