Study Of The Inactivation Effects And Mechanism Of High Pressure Carbon Dioxide On Bacillus Subtilis Spores

Sterilization is an important link of food processing. As the conventional method forsterilization, thermal processing is easy and efficient. However, it will bring adverse effectsto the color, taste, texture and nutrition of food. Therefore, the research of the non-thermalsterilization technology （HPCD） is necessary. High pressure CO₂has a significant lethaleffect on the microorganisms, and it has no pollution. Low cost and preserved original flavorafter treatment make the HPCD sterilization technology become the focus of the athermalsterilization technologies.Spores, as bacterial dormancy body, have higher resistance to the heat, pressure, andradiation, so the lethal effect of spores is often taken as a criterion of food sterilization effect.This paper took the common bacillus subtilis spores as subjects. First, response surfaceexperimental was used to analyze and optimize the process of HPCD. Then, the mechanismof killing spores by HPCD was studied by SEM and HPLC. At last, on the basis of the aboveand previous studies, an efficient method that something cooperated with HPCD which had alower cost was attained and orange juice was taken as applications by this method, whenUHT was taken to have a contrast, so as to study its practicability. The results showed that:1) HPCD had a good sterilization effect to the spores, while pressure, temperature asvery significant influencing factors, and dwell time as significant influencing factor. Therange of the three parameters combination from the response surface analysis software was25.6²8.8MPa,40⁴7℃,36.5⁴7min, while the lethal logarithmic could reach3.48.2) In allusion to the mechanism of killing spores by HPCD, it was found the effect ofsterilization improved significantly when added with germination agents, but the sporegermination inhibitors had adverse effects. Therefore, it was guessed that HPCD mainlykilled spores that had germinated. N2was used to substitute CO₂for processing experimentsat the same condition, and the result showed that the lethal effect of the CO₂treatment groupwas obviously higher than that of N2and there were more rupture, internal leakage, etc. in thespores of the HPCD treatment group. All the above demonstrated only mechanical crushingmechanism could not explain the spores’ death. For the mechanism of acidification, theexperiments found it was pH6that had the best sterilization effect, not the lower the better,so it was proved external acidification lethal mechanism was not enough to explain themechanism of killing spores by HPCD, however, when the spores germinated into vegetative mass in the near neutral conditions, its internal acidification mechanism might be the cause ofits death.3) Orange juice was taken as applications by HPCD treatment which was cooperatedwith germination agent—inositol+L–alanine and the natural bacteriostatic agent—nisin,when UHT was taken to have a contrast. Finally, it was found that both HPCD and UHTcould make the orange juice achieve national food safety standards; there was little differencein the pH and the total acid after the two kinds of processing methods, but the VCcontent gotgreat damage after UHT, which fully showed the superiority of fruit juice sterilization byHPCD.