Abstract
In the present study, the synergetic effect and mechanism of ultrasound (US) and slightly acidic electrolyzed water (SAEW) on the inactivation of Escherichia coli (E. coli) were evaluated. The results showed that US combined with SAEW treatment showed higher sanitizing efficacy for reducing E. coli than US and SAEW alone treatment. US and US combined with SAEW treatments resulted in smaller particle size of E. coli compared to the control and SAEW treatment. In addition, US combined with SAEW treatment induced the highest potassium leakage. However, the highest protein leakage was recorded in US treatment. Moreover, scanning and transmission electron microscopy analysis revealed that the greatest damage of the appearance and ultrastructure of E. coli was achieved after US combined with SAEW treatment. The synergetic effect was also confirmed by CLSM analysis. Fluorescence spectroscopy suggested that treatments of US, SAEW, and US combined with SAEW changed protein conformation of E. coli. Overall, the present study demonstrated that the sterilization mechanism of US combined with SAEW treatment was decreasing the particle size and disrupting the permeability of cell membrane and the cytoplasmic ultrastructure as well as changing protein conformation of E. coli.
Highlights
Escherichia coli (E. coli), a Gram-negative rod-shaped bacterium, is widely recognized as one of the major food-borne pathogens often from the consumption of contaminated foods [1, 2]. erefore, a great variety of sanitization strategies, including heating, ultrasound, ultraviolet-C, sodium hypochlorite, sodium benzoate, potassium sorbate, chlorine dioxide, and so on, have been used to reduce the microbial population and prolong the shelf life of food products by the food industry [3,4,5]
Our results showed that ultrasound produced micro-cracks in the bacterial cell membranes, allowing NaOCl into the cells, and Journal of Food Quality deactivated E. coli and reduced the usage amount of sodium hypochlorite [9]
Effect of US Combined with slightly acidic electrolyzed water (SAEW) Treatment on the Microbicidal Efficiency and Particle Size Distribution
Summary
Escherichia coli (E. coli), a Gram-negative rod-shaped bacterium, is widely recognized as one of the major food-borne pathogens often from the consumption of contaminated foods [1, 2]. erefore, a great variety of sanitization strategies, including heating, ultrasound, ultraviolet-C, sodium hypochlorite, sodium benzoate, potassium sorbate, chlorine dioxide, and so on, have been used to reduce the microbial population and prolong the shelf life of food products by the food industry [3,4,5]. Erefore, a great variety of sanitization strategies, including heating, ultrasound, ultraviolet-C, sodium hypochlorite, sodium benzoate, potassium sorbate, chlorine dioxide, and so on, have been used to reduce the microbial population and prolong the shelf life of food products by the food industry [3,4,5]. A more effective and much safer sterilizing technology is crucial for environmental conservation and food preservation. Ultrasound, as a promising non-thermal sterilization technique, can cause physical effects and/or chemical effects, decontaminating microorganisms from the surfaces of foods. Koda et al [6] reported that inactivation of microorganisms by high frequency ultrasound was mainly dependent on the chemical effects. Many literatures reported that sterilization effect of combined treatment of ultrasound with chemical sterilant was more effective than each used alone [8]. Our results showed that ultrasound produced micro-cracks in the bacterial cell membranes, allowing NaOCl into the cells, and
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