Antimicrobial mechanism of pulsed light for the control of Escherichia coli O157:H7 and its application in carrot juice

As a non-thermal sterilization method, pulsed light (PL) has been widely applied in food industries to control the microbial contamination, however little is known about the antimicrobial mechanism of PL. This study deeply investigated the antimicrobial mechanism of PL against Escherichia coli 0157:H7 (E. coli O157:H7). The changes of morphology, endoenzyme, entocyte, respiratory metabolism and DNA of E. coli O157:H7 after PL treatment were emphatically studied. TEM and SEM results exhibited that cell integrity was destroyed heavily after PL treatment. Entocyte including proteins, ATP and DNA were reduced remarkably for PL-treated samples. In addition, the activity of ATPase, beta-galactosidase, alkaline phosphatase, topoisomerase, as well as the metabolism were inhibited for E. coli O157:H7 with PL treatment. The electron spin resonance spectrum validated the production of hydroxyl radical by PL, thus resulting in the elevation of intracellular reactive oxygen and the acceleration of cell death. Finally, PL displayed better antibacterial activity in carrot juice without adverse effect on its quality.