Sterilization of Food Powder by Flash Discharge of High-Pressure Gas

本文研究了一种新型的高压二氧化碳非热杀菌方法。在第一年，即1993年，测定了不同温度、压力、处理时间、减压速率和水分条件下对酵母细胞和细菌孢子的致死作用。在40bar、40ﾟC条件下，将水分含量大于60%的湿酵母细胞(Saccharmyces Cerevisiae)浸泡在高溶于水的CO2气体中3h以上，然后突然释放压力，即被完全破坏。巨大芽孢杆菌QMB1551经70巴、60ﾟ℃CO2处理24小时后，内孢子存活率可降至4×10~(-4)。CO_2的吸附和解吸可能是影响微生物细胞和孢子脱氢的关键现象。这些生物的死亡不仅仅是减压时的机械破裂造成的，高压二氧化碳本身的致死作用也可以在治疗过程中发挥作用。1994年研究了CO_2、N_2O、N_2和Ar的杀菌效果，发现N_2O也是酵母细胞死亡的有效气体。然而，除CO_2外，其他气体对孢子的灭菌效果不佳。最适压力似乎出现在去年处理孢子时的临界CO_2压力附近。今年的额外实验证实了这一点，但最佳压力的原因尚不清楚。用这种方法处理酵母细胞，胞内蛋白的萃取率提高了20%，但对孢子的萃取率并没有提高。

This is a research on a novel non-thermal sterilization method using high-pressure carbon dioxide. In the first year, that is, 1993 the lethal effect on yeast cells and bacterial spores were tested under the different condition of temperature, pressure, treatment time, decompression rate and water content. The wet yeast cells (Saccharomyces cerevisiae) with more than 60 % water content were completely destroyed , when the organisms were saturated with CO_2 gas, highly soluble in water, at 40 bar and 40ﾟC for more than 3 hr and then the pressure was suddenly released. The survival ratio of the endospores of Bacillus megaterium QMB 1551 could be reduced to 4*10^<-4> after the CO2treatment at 70 bar and 60ﾟC for 24 hr. It was expected that sorption as well as desorption of CO_2 could be the crucial phenomena to influence the deahth of microbial cells and spores. The death of the organisms was not produced only by mechanical rupture at the time of decompression, and the lethal effects of high-pressure CO_2 itself could work during treatment. In 1994 the bactericidal effects of CO_2, N_2O,N_2 and Ar was examined, and it was found that N_2O was also an effective gas for death of yeast cells. The gases other than CO_2 was, however, not effective for sterilization of the spores. The optimum pressure seemed to appear near the critical pressure of CO_2, when the spores were treated last year. This was confirmed this year by the additional experiments, but the reason for the optimum pressure was not clear. The treatment of the yeast cells by this method produced an increase in extraction of intracellurar proteins by 20 %, but the extraction was not improved in case of the spores.