1. Radiation Sterilization and Preservation Mechanism The heat sterilization commonly used in food packaging is based on increasing the ambient temperature to exceed the tolerance of the bacteria, and eventually achieve the goal of eliminating bacteria. Open-wave sterilization relies on electromagnetic waves to give vibrational energy to bacterial molecules, which in turn causes bacterial molecules to move and produce frictional heat that kills bacteria.
The sterilization effect of ionizing radiation was discovered about a hundred years ago. Sterilization theory mainly includes target theory and metabolic theory. The classic damage mechanism is “target theoryâ€: cells have a life center—deoxyribonucleic acid molecule. If high-energy ray particles hit this “targetâ€, the cells Will die. The modern theory of "structural metabolism theory" believes that under irradiation of radiation, biofilms are damaged and fatty acids and cesium peroxides are formed. These toxins can cause serious secondary damage to the genetic organs of cells and eventually lead to the death of bacteria.
2. Radiation Sterilization Fresh-keeping effect studies have shown that radiation sterilization effects generally vary with the type of microbe, number of bacteria, physiological state, irradiation temperature, environmental composition, and coexisting substances. Gram-positive bacteria are far more resistant than gram-negative bacteria in spore-free bacteria; sporulated bacteria are generally more tolerant than spore-free bacteria, and spores are particularly resistant to radiation. In fungi, mold and yeast are strong. The D value of various microorganisms (irradiation dose when the number of remaining cells is one-tenth when irradiated by irradiation) is approximately between 0.02-0.6 (X104GY).
3. Influencing Factors of Irradiation Sterilization and Preservation In general, the factors affecting the sterilization effect include ambient temperature, gas composition, and bacterial concentration. In terms of temperature, D value generally increases with decreasing temperature. Therefore, when the irradiation is performed under heating conditions, the germicidal effect is enhanced. For example, when the ambient temperature at the time of irradiation exceeds 65° C., the D value of Botox decreases abruptly. Therefore, the simultaneous use of heating and irradiation is an effective means to increase the sterilization effect of irradiation.
If oxygen is present during irradiation, the damage of the organism will increase and the sterilization effect will increase. If the Bacillus spores are exposed to nitrogen, their D value will be about twice that in the air. The concentration of microorganisms is also one of the influencing factors. The concentration of bacteria increases, the resistance to radiation is also enhanced, and the sterilization effect is worse.