Thermal death

Craig D B, Arriaga E A, Wong J C Y, Lu H and Dovichi N J 1996 Studies on single alkaline phosphatase molecules reaction rate and activation energy of a reaction catalyzed by a single molecule and the effect of thermal denaturation—the death of an enzyme J. Am. Chem. See. 118 5245-53... 

A convenient multiple of D is the thermal death time F. It is the exposure time required for less than 1 x 10 probabiUty of survival (4,5). The relationship between F and becomes equation 7 ... 

As predicted by the Arrhenius equation (Sec. 4), a plot of microbial death rate versus the reciprocal or the temperature is usually linear with a slope that is a measure of the susceptibility of microorganisms to heat. Correlations other than the Arrhenius equation are used, particularly in the food processing industry. A common temperature relationship of the thermal resistance is decimal reduction time (DRT), defined as the time required to reduce the microbial population by one-tenth. Over short temperature internals (e.g., 5.5°C) DRT is useful, but extrapolation over a wide temperature internal gives serious errors. 

The activation energy (E) associated with microbial death is larger than the thermal inactivation of chemical compounds in fermentation broths (see Table 24-4). Thus by sterthzing at high temperatures for short times (HTST), overcooking of nutrients is minimized. 

Chemical PPE In a fire or thermal energy hazard, PPE worn by responders should meet, at a minimum, the criteria in 29 CER 1910.156 (e), Eire Brigade Standard, requiring turnout gear. In conditions where skin absorption of a hazardous substance may result in substantial possibility of immediate death, serious illness, or injury or impaired ability to escape, totally encapsulated chemical protective suits should be used. It is vital to keep heat resistance of the totally encapsulated suits and the heat resistance of any PPE used underneath or in conjunction with the totally encapsulated suits in mind any time there is a thermal hazard. 

Death kinetics are obviously important in chemical or thermal sterilization. The spores formed by some bacteria are the hardest to kill. Problem 12.3 gives data for a representative case. 

Wang et al. report the death kinetics of Bacillus stearothermophilus spores using wet, thermal sterilization. Twenty minutes at 110°C reduces the viable count by a factor of lO". The activation temperature, E/Rg, is 34,200 K. How long will it take to deactivate by a factor of lO ... 

Highly toxic perfluoroisobutylene (PFIB) poses a serious health hazard to the human respiratory tract. PFIB is a thermal decomposition of polytetrafluo-roethylene (PTFE), e.g., Teflon. PFIB is approximately lOx as toxic as phosgene. Inhalation of this gas can cause pulmonary edema, which can lead to death. PFIB is included in Schedule 2 of the Chemical Weapons Convention (CWC), the aim of the inclusion of chemicals such as PFIB was to cover those chemicals, which would pose a high risk to the CWC. 

Nitrogen containing polymers have the potential to release cyanide when thermally decomposed. This study demonstrates that cyanide plays an important role in fire deaths. 

Pullman GS, DeVay JE, Garber RH (1981a) Soil solarization and thermal death a logarithmic relationship between time and temperature for four soilbome plant pathogens. Phytopathology... 

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