1996 Volume 43 Issue 10 Pages 1138-1145
It has been observed that the sterilizing effect of the steam injection type direct heating sterilizer has been less than the apparent sterilizing effect which is estimated from the holding time and the temperature in the holding tube section. Because this type sterilizer sterilizes the product momentarily at an ultrahigh temperature only in the holding tube, the behavior of the steam and product with holding tube has a significant impact on the sterilization effect. In order to determine the factors which may reduce the sterilization effect within the holding tube, microbiological tests were carried out using a laboratory machine (100l/h) and a practical machine (2150l/h). This tests were conducted with soybean milk inoculated with Clostridium sporogenes PA3679 spores. It was observed that cyclical fluctuations of temperature occured in the holding tube. Calculations, estimated from data obtained from measuring the fluctuations, revealed that the fluctuations clearly had an impact on the sterilization effect and was a factor in reducing the accuracy of the apparent sterilization effect. Accordingly this must be fully taken into consideration when setting the sterilization conditions.
