Effect Of X-ray Irradiation On The Sterilization Of Fresh Beef

The irradiation is a physical method which uses the atomic energy beam's exposure energy to sterilize food. Due to its characteristics of environmental protection, safety and high efficiency, this method that can efficiently restrain or eliminate pathological and spoiled organisms has been applied in sterilization and preservation of food. Radiation sources of food irradiation technology includeγ-ray, electron beam and X- ray. X-ray not only has characteristics of controllability of electron accelerator and non radioactive sources, but also has strong penetrating power. It has a certain significance that explore X-ray irradiation sterilization for the development of food irradiation technology. Kilogray(kGy) of irradiation dose was used for the study at present. Sterilization effect of fresh beef with gray(Gy) of irradiation dose by X-ray was emphatically discussed in this paper.Low power X-ray irradiator was used to irradiate the microorganisms in contaminated fresh beef from 3.08 to 18.48 Gy. D₁₀ values were gained by correlation analysis of microbial survival rate and irradiation dose in this condition. The radiation sensitivity of them was also discussed. The results showed that: the D₁₀ values for environmental polluted bacteria strains of Escherichia coil, Bacillus cereus and its spores, Bacillus subtilis and its spores were 5.41, 5.00, 23.81, 5.68, 21.74 Gy respectively, the D₁₀ values for pathogenic bacteria strains of Staphylococcus aureus and Listeria monocytogenes were 5.35 and 6.45 Gy respectively, the D₁₀ values for spoilage bacteria strains of Pseudomonas fluorescens, Pseudomonas aeruginosa, Lactobacillus palantarum , Shewanella. putrefaciens and Penicillium were 3.62, 4.39, 4.70, 8.20, 16.39 Gy respectively. Among the strains tested, spores of Bacillus cereus and Bacillus subtilis, Penicillium were more resistant to radiation, Pseudomonas fluorescens and Pseudomonas aeruginosa were more sensitive to radiation. After irradiated by low power X-ray, the strains tested still had some bactericidal effects.Uninoculated and inoculated fresh beef samples were irradiated from 4.42 to 19.89 Gy. The D₁₀ values of total number of bacterial colony, Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa and Lactobacillus palantarum in fresh beef were 10.10, 11.50, 14.50, 11.11, 13.89 Gy respectively by correlation analysis of microbial survival rate and irradiation dose in this condition. The total number of bacterial colony in fresh beef was most sensitive to radiation, Staphylococcus aureus and Pseudomonas aeruginosa were more sensitive to radiation than Listeria monocytogenes and Lactobacillus palantarum. Due to the impact of radiation on Escherichia coil is very small, its D₁₀ value in fresh beef was not gained.Strains of Staphylococcus aureus, Listeria monocytogenes and vibrio parahaemolyticus in pure culture samples were irradiated from 0.5 to 3.0 hour. Photon numbers of samples received were obtained by calculation in different time.The results showed that: the population of the three pathogens had different degrees of decline. Compared with Staphylococcus aureus and Listeria monocytogenes, the downward trend of vibrio parahaemolyticus was obvious. It could be concluded that the more photon numbers the samples recieved, the better the sterilization effect during a certain time.The low power and low dose of X-ray was used to irradiate the microorganisms in contaminated fresh beef, Among the strains tested, radioresistance of spore-forming bacteria were relatively stronger, second were mold, non-spores bacteria were least resistant. Uninoculated and inoculated fresh beef after irradiated by X-ray, the total number of bacterial colony in fresh beef was most sensitive to radiation, Staphylococcus aureus and Pseudomonas aeruginosa in fresh beef were more sensitive to radiation, Listeria monocytogene and Lactobacillus palantarum were less sensitive to radiation.