Kinetic Parameters for Inactivation of Bacillus stearothermophilus at High Temperatures

Abstract

High temperature thermal death parameters for Bacillus sfearofhermophilus TH24 (NCDO 1096) spores in water were determined using a computer-controlled reactor. The equipment produced and recorded accurate, reproducible square-wave temperature transients during very short heating times (-0.1 set). Survivor curves and the phantom thermal death time (TDT) curve between 130°C and 155°C from reactor data were compared to results from oilbath-heated capillary tubes between 115°C and 135°C. The TDT curve was nonlinear in the high temperature range but could be described by two lines with z = 9.3C for temperatures between 115°C and 145°C and z = 16.9C" for temperatures above 145°C. An Arrhenius plot did not represent the data better.

Characterization of Bacillus sporothermodurans IC4 spores; putative indicator microorganism for optimisation of thermal processes in food sterilisation

“…1 and 2). This data corroborates previous studies and confirms that it is a common phenomenon in highly heatresistant bacterial spores (Cook & Brown, 1965;David & Merson, 1990). Different models were used to fit shoulders.…”

“…The tubes were then sealed by flame and heated in a stirred oil bath at 117, 119, 121, 123, and 125°C, for various times of exposure. The come-up time was less than 6 s, therefore it was not taken into account since exposure times were always above 30 s (David & Merson, 1990). After the treatment, the tubes were cooled immediately in ice/water, washed, and both ends were clipped off under sterile conditions.…”

“…These methods have been extensively used and described in the scientific literature, e.g. Clostridium sporogenes PA3679 (Ocio, Sánchez, Fernandez, Rodrigo, & Martínez, 1994) or Bacillus stearothermophilus strains (David & Merson, 1990).…”

Impact of dissociation equilibrium shift on bacterial spore inactivation by heat and pressure

“…The different non-linear inactivation characteristics after thermal and pressure treatment have been discussed by Table 1 Initial pH-value and Weibullian power law parameter (b, n, R 2 ) for inactivation kinetics of G. stearothermophilus in ACES and phosphate buffer after different treatments (Curran & Evans, 1945;David & Merson, 1990;Finley & Fields, 1962;Humphrey & Nickerson, 1961;Hyatt & Levinson, 1968;Keynan, Evenchik, Halvorson, & Hastings, 1964;Shull, Cargo, & Ernst, 1963). Humphrey and Nickerson (1961) explained the initial phase by a heatinduced initiator, which could be thought of as being divided in a less heat-labile and inactive state from which it would be freed by heat but eventually destroyed by further heating.…”

Impact of agglomeration on the quantitative assessment of Bacillus stearothermophilus heat inactivation

“…For calculation of the temperature profile in the capillary Stern, Herlin, and Procter (1952) demonstrated that the heat penetration characteristic is the same like of an infinite (length) cylinder. A common method is to measure the temperature with a fine wire thermocouple centred in the capillary tube (David & Merson, 1990), but it should be pointed out that the response time of the thermocouple must be subtracted. Olson and Schultz (1942) created tables for the numerical solution of the heating equations.…”