Analysis of variations in microbial heat resistance and its application to predictive theory in non-isothermal heat sterilization

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10650790
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 生物・生体工学
• Research Institution: Kansai University
• Principal Investigator: TSUCHIDO Tetsuaki Kansai University, Faculty of Engineering, Professor, 工学部, 教授 (50029295)
• Co-Investigator(Kenkyū-buntansha): MATSUMURA Yohsinobu Kansai University, Faculty of Engineering, Lecturer, 工学部, 専任講師 (40268313)
• Project Period (FY): 1998 – 1999
• Keywords: pasteurization of food / nonisothermal process / Escherichia coli / heat resistance / preincubation

Research Abstract

To establish the microbiological safety of heat-processed foods, the development of reliable method for designing process evaluation is necessary. In this study, we analyzed the reaction of an increase in the heat resistance of Escherichia coli cells in the nonisothermal process and used the results obtained from this approach for the construction of database on thermal death, and we further aimed to apply the whole information to the prediction food pasteurization process.
In the fiscal 1998, we investigated the effect of dilution rate in the rising temperature process just before the isothermal heat treatment on the heat resistance of E. coli. A 100-fold dilution caused a discontinuous sharp change at about 22℃ in the dependency of the resistance on the preincubation temperature, whereas, in the case of a 10-fold dilution, the resistance was decreased gradually with decreasing temperature for preincubation below about 22℃.
In the fiscal 1999, we analyzed the process of the increase in the resistance during the preincubation period using the heating system of 100-fold dilution. The initial rate of an increase in D value depended upon the preincubation temperature. Above 15℃, The final level of D value after prolonged preincubation treatment was similar about 15 to 37℃, being about 60 sec, but very low at 10℃.
The results obtained indicate that the preincubation process and the rising temperature process affect profoundly the thermal death during the subsequent isothermal heat process. In relation to this study, we also carried out the database construction on the thermal death of E. coli cells exposed to various heating conditions, including temperature, pH, and NaCl concentration.