本研究研究了过硫酸铵(PS)和超声(US)对缓冲蛋白胨水(BPW)和橙汁产品中大肠杆菌O157:H7的协同作用。PS浓度范围从1到300mM的综合评估,不仅考虑了统计意义,而且考虑了实验结果的可靠性和稳定性,表明150mM是灭活大肠杆菌O157:H7的最佳PS浓度。此外,评估了最大US强度的30%至60%的US输出强度,发现50%US振幅是最佳US条件。超声波仪上的50%振幅设置对应于其最大位移的一半,大约60μm,基于120μm的最大振幅。大肠杆菌O157:H7的灭活水平通过PS和US的联合处理显著提高,与单独使用PS和US的每种治疗方法相比。在BPW中,PS和US的组合10分钟的治疗导致显著的协同失活,达到3.86logCFU/mL的对数减少。同样,在橙汁产品中,用PS和US的组合进行5分钟的处理产生了显着的协同失活,降低达到5.90logCFU/mL。尽管该处理引起了样品中的显著颜色变化,治疗组和非治疗组之间的视觉差异不明显.此外,与BPW相比,橙汁中的联合治疗显示出显着增强的抗菌功效。尽管相同的5分钟治疗时间,在橙汁中的应用导致大肠杆菌O157:H7的对数大幅减少,在降低的PS浓度为30mM时达到7.16对数CFU/mL,而在BPW中相同的处理在PS浓度为150mM时仅产生2.89logCFU/mL的降低,从而突出了其在橙汁中显著优越的抗菌性能。微生物灭活的潜在机制,由PS和US联合治疗诱导,被鉴定为显著的细胞膜损伤。这种损伤是由硫酸根介导的,通过过硫酸盐的声波活化产生。此外,橙汁的低pH值,与BPW(pH7.2)相比,在3.7处测得的大肠杆菌O157:H7细胞可能进一步恶化,通过破坏它们的细胞膜,质子梯度,和能量代谢。这些发现强调了PS和US集成作为食品工业中非热巴氏灭菌的有希望的方法的有效性。需要进一步的研究来优化处理参数,并充分探索该技术在大规模食品加工操作中的实际应用。感官评估和营养评估对于解决PS的局限性也是必要的。
This study investigated the synergistic effects of ammonium persulfate (PS) and ultrasound (US) on the inactivation of Escherichia coli O157:H7 in buffered peptone water (BPW) and orange juice products. A comprehensive assessment of PS concentrations ranging from 1 to 300 mM, considering not only the statistical significance but also the reliability and stability of the experimental outcomes, showed that 150 mM was the optimal PS concentration for the inactivation of E. coli O157:H7. Additionally, US output intensities varying from 30 % to 60 % of the maximum US intensity were evaluated, and 50 % US amplitude was found to be the optimal US condition. A 50 % amplitude setting on the sonicator corresponds to half of its maximum displacement, approximately 60 μm, based on a maximum amplitude of 120 μm. The inactivation level of E. coli O157:H7 was significantly enhanced by the combined treatment of PS and US, compared to each treatment of PS and US alone. In the BPW, a 10-min treatment with the combination of PS and US resulted in a significant synergistic inactivation, achieving up to a log reduction of 3.86 log CFU/mL. Similarly, in orange juice products, a 5-min treatment with the combination of PS and US yielded a significant synergistic inactivation, with a reduction reaching 5.90 log CFU/mL. Although the treatment caused a significant color change in the sample, the visual differences between the treated and non-treated groups were not pronounced. Furthermore, the combined treatment in orange juice demonstrated significantly enhanced antimicrobial efficacy relative to BPW. Despite identical 5-min treatment periods, the application in orange juice resulted in a substantially higher log reduction of E. coli O157:H7, achieving 7.16 log CFU/mL at a reduced PS concentration of 30 mM, whereas the same treatment in BPW yielded only a 2.89 log CFU/mL reduction at a PS concentration of 150 mM, thereby highlighting its significantly superior antimicrobial performance in orange juice. The mechanism underlying microbial inactivation, induced by the combined treatment of PS and US, was identified as significant cell membrane damage. This damage is mediated by sulfate radicals, generated through the sono-activation of persulfate. In addition, the low pH of orange juice, measured at 3.7, is likely to have further deteriorated the E. coli O157:H7 cells compared to BPW (pH 7.2), by disrupting their cell membranes, proton gradients, and energy metabolism. These findings underscore the effectiveness of PS and US integration as a promising approach for non-thermal pasteurization in the food industry. Further research is needed to optimize treatment parameters and fully explore the practical application of this technique in large-scale food processing operations. Sensory evaluation and nutritional assessment are also necessary to address the limitations of PS.