Sterilization Effect and Mechanism of Negative Ions in Refrigerator

In this study, Staphylococcus, Candida and Penicillium that had been isolated and purified from commercial salmon, chicken breast and citrus in our laboratory were used as target microorganisms to explore the sterilization effect and mechanism of applying negative ions in the 4 ℃ cold storage room of a refrigerator. The results showed that negative ion treatment was effective in killing Staphylococcus, Candida and Penicillium in the cold storage room, and this effect increased with sterilization time (when the sterilization time was extended from 0.5 to 2 h, the sterilization efficiency of negative ions on Staphylococcus increased from 92.61% to 99.29%, and the sterilization efficiency on Candida from 61.45%to 98.26%; when the sterilization time was 1 h, the colony growth of Penicillium could be completely inhibited). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation showed that negative ion treatment disrupted the structure of Staphylococcus, Candida and Penicillium cells, resulting in leakage of intracellular contents. After this treatment, the conductivity and absorbance values at 260 and 280 nm of the suspensions of Staphylococcus, Candida and Penicillium increased significantly, indicating that their cell integrity was damaged, resulting in leakage of intracellular nucleic acids and proteins. Fluorescein diacetate (FDA) staining showed that negative ion treatment significantly decreased the cell vitality of Candida and Penicillium. In addition, it completely inhibited the spore germination and germ tube formation of Penicillium. Therefore, negative ion treatment in the cold storage room of a refrigerator can destroy the cell integrity of Staphylococcus, Candida and Penicillium, reduce the cell vitality of Candida and Penicillium, and inhibit the spore germination and germ tube formation of Penicillium, thereby effectively killing these target microorganisms.