Thermal Death Determination: Design and Evaluation of a Thermoresistometer

Abstract

The design and performance of a thermoresistometer (TR-SC) are described. This instrument has a high heating (57"C/sec) and cooling rate and can be used to determine spore survival curves at temperatures up to UHT range. Spores can be heated in homogenized foods under constant monitoring-of pH (f 0.001 u.pH) and-stable temperatures (t O.l"C). D, values can be determined to 0.008 min. This method iakes less'timk and effort than by capillaries. The fit of D, values to thermal death time curves (TDT) curves is better by the TR-SC than by the capillary method. Survival and TDT curves for Bacillus lichenifomis Bacillus coagulans and Bacillus subtilis were determined in homogenized foods and in McIlvaine buffer at tempertures up to the UHT range.

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

“…The standard capillary technique can not be used at temperatures above 125°C due to the come-up time associated with this indirect heating system and the short exposure times required at high temperatures. In contrast, the thermoresistometer allows to perform studies up to 125°C (or even higher) and takes less time and effort (Condón, López, Oria, & Sala, 1989). Unfortunately, the method used to generate survival curves data had an effect on the length of shoulders.…”

Peroxidase Stability and Reactivation after Heat Treatment and Manothermosonication

“…Heat treatments were performed in a TR-SC thermoresistometer (Condon et al, 1989). Manothermosonication was carried out in a thermoultrasonic resistometer made by a modification of the TR-SC instrument as described by Lopez et al (1994).…”

Nonisothermal heat resistance determinations with the thermoresistometer Mastia

“…Many different heat resistance determination methods have been used (Stumbo 1973; Brown and Ayres 1982), each of them having their own advantages and drawbacks. In 1989 Condón et al. built the thermoresistometer TR‐SC, later improved in 1993, where most advantages of the existing methods were incorporated: heating lags were avoided because a small inoculum volume (0·2 ml) was mixed with a large volume of heating menstruum (350 ml) and cooling lags were also avoided because small sample volumes were taken each time from the vessel, and then were immediately cooled; heat resistance in homogenized foods was enabled using a wide enough sampling tube; the estimation of heat resistance was possible in a wide range of temperatures, from pasteurization to UHT, because the thermoresistometer was pressurized, under constant monitoring of pH, and determination of D T ‐values as low as 0·0009 min was possible by means of a sample collector (for Bacillus coagulans at 138°C; Condón et al.…”