Dual functionality of ultrasound-CaCl2-slightly acidic electrolyzed water: Efficient Salmonella Thompson reduction and onion freshness retention

Abstract

This study explores the synergistic antibacterial effects of ultrasound (US) combined with calcium chloride-slightly acidic electrolyzed water (CaCl₂-SAEW) against Salmonella Thompson and the application in the cleaning and preservation of sliced onions. The results showed that the antimicrobial effect of US + CaCl₂-SAEW was superior to the single treatment. A treatment of 161 W/cm² US combined with 1.5 mg/L CaCl₂-SAEW for 10 min reduced S. Thompson populations from 7.63 ± 0.15 CFU/mL to 2.71 ± 0.04 log CFU/mL. The antimicrobial mechanism was elucidated through an in-depth investigation of the destabilizing effects of CaCl₂-SAEW on bacterial membranes induced by US. N-Phenyl-l-naphthylamine and flow cytometry showed that US enhanced the exacerbation of CaCl₂-SAEW on the permeability changes and disruption of the integrity of S. Thompson cell membranes. Field emission scanning electron microscope observed irreversible damage to the structure of cell membranes by US + CaCl₂-SAEW. In addition, US + CaCl₂-SAEW significantly (p < 0.05) enhanced the storage efficacy of onion slices. Ca⁺² played a key role in mitigating the quality deterioration of onions during storage, highlighting the dual function of Ca⁺² in enhancing the antimicrobial efficacy and maintaining the quality of the product with US + SAEW. These findings suggest that US + CaCl₂-SAEW offers a promising application strategy for the cleaning and preservation of fresh-cut fruits and vegetables.