Continuous Inactivating Shiga-toxin Producing E. coli in Milk By a Liquid-phase Plasma Process

In this study, we demonstrate that treating milk using a continuous liquid-phase plasma (CLPD) based process is an effective solution. The effect of different system power (180 W-320 W) and flow rate (30 ml/min-70 ml/min) on the inactivation of Shiga-toxin Producing E. coli (STEC) enriched in pasteurized milk was evaluated. Pasteurized milk without STEC enrichment served as a parallel control. Experiments have shown that CLPD-treated milk exhibits a significant reduction in colony-forming units (CFU) of STEC under majority of treatment conditions based on the two significant operational factors. It has been proven that system power and liquid flow rate significantly impact continuous microbial inactivation in milk. A lower flow rate (30ml/min) and higher system power (300w) result in a notable CFU reduction (6.3 logs), while the higher flow rates with lower system power led to milder changes in STEC reduction in milk. Under strong treatment conditions, the STEC inactivation effect was consistent with low variation. Evaluation of the physicochemical properties of CLPD treated milk revealed lower resultant temperatures compared to conventional pasteurization methods. Scanning Emission Microscopy (SEM) imaging has revealed significant cell disruption of STEC by CLPD processing. These findings offer practical insights into cold plasma treatment of milk, suggesting it as a potential alternative to conventional pasteurization methods.