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灭菌方法。在第一年即1993年，在不同的温度、压力、处理时间、减压速率和含水量条件下，测定了对酵母细胞和细菌孢子的致死作用。在40巴、40 ℃下，用高溶于水的CO_2气体饱和酵母细胞3小时以上，然后突然减压，可使含水量大于60%的湿酵母细胞完全破坏。巨大芽孢杆菌（Bacillus megaterium）QMB 1551在70 bar、60 ℃条件下处理24 h后，其内生孢子的存活率可降至4 × 10 ~（-1）%<-4>，CO_2的吸附和解吸可能是影响微生物细胞和孢子死亡的关键现象。生物体的死亡并不仅仅是由于减压时的机械破裂造成的，高压CO_2本身的致死作用也可以在处理过程中发挥作用。1994年对CO_2、N_2O、N_2和Ar的杀菌效果进行了研究，发现N_2O也是一种有效的致死酵母细胞的气体。除CO_2外，其它气体对孢子无杀菌作用。最适压力似乎出现在CO_2临界压力附近，去年处理孢子时。这一点在今年的附加实验中得到了证实，但最佳压力的原因尚不清楚。用这种方法处理酵母细胞使胞内蛋白质的提取增加了20%，但在孢子的情况下提取没有改善。

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.