Spores inactivation

Humidity can be a problem. Whereas it was shown (284) that 33% RH was best for spore inactivation, and that at least 30% RH was needed for effective sterilisation (285), dried spores are difficult to kill, and the spore substrate material and wrappings compete with the spore for the available moisture (286). Therefore, the relative humidity is adjusted to 50—70% to provide sufficient moisture for the spores to equiUbrate. The exposure time depends upon the gas mixture, the concentration of ethylene oxide, the load to be sterilised, the level of contamination, and the spore reduction assurance requited. It may be anywhere from 4—24 hours. In a mn, cycles of pre-conditioning and humidification, gassing, exposure, evacuation, and air washing (Fig. 9) are automatically controlled. 

Heat-resistant fibers, 23 389 Heat-resistant spores, inactivation of, 22 79... 

Ultra-high-temperature treatment (UHT) is now the most widely exploited method in the food industry to stabilize microbiologically any foodstuff. It consists of heating at an ultra high-temperature for a short period of time for example, a treatment at 145°C for 2 seconds is sufficient to assure a total microbial- and spore inactivation. The microbial death is principally due to irreversible cell damage (e.g., of proteins, DNA, RNA, vitamins) enzymes are inactivated by heat which modifies their active sites. 

In 1990, Halbauer [16] demonstrated the existence of a minimum value of pressure for spore-inactivation and in the same year Ludwig s group [17, 18] stressed that, in order to kill the spores, it seemed necessary to germinate them first. 

The inactivation of spores by CO2 has been described by a single first-order rate constant (54,57). In contrast, a two-step process has been reported for the heat inactivation of spores in the absence of CO2 (54,59). The presence of CO2 during heat treatment could increase the rate of spore heat activation, considered to be an initial step in sterilization (59), and/or the rate of spore inactivation to result in first-order sterilization kinetics (54). 

Mueller, W.D. and Dederer, I. 2008. Spore inactivation in cooked sausage with combined high pressure and heat treatment. Fleischwirtschaft 88 99-102. 

The bactericidal activity of formaldehyde, and formaldehyde-releasing disinfectants, is influenced significantly by temperature, with extensive spore inactivation at temperatures of 40°C and above [75-77]. pH does not seem to influence the antimicrobial efficacy of formaldehyde, or any other aldehyde with the notable exception of glutaraldehyde [8]. 

Hayakawa, I. Kanno, T Tomita, M. Fujio, Y. Application of high pressure for spore inactivation and protein de-naturation. J. Food Sci. 1994, 59, 159-163. 

Sporicide kills (inactivates) bacterial spores, and is therefore expected to kill all other microorganisms of less resistance. According to the AO AC International it may not kill 100% of the spores, and therefore may not be as powerful as a sterilant. However, according to the EPA, sporicide and sterilant are considered identical. 

At 70—140°C, peroxide is vaporised. Peroxide vapor has been reported to rapidly inactivate pathogenic bacteria, yeast, and bacterial spores in very low concentrations (133). Experiments using peroxide vapor for space decontamination of rooms and biologic safety cabinets hold promise (134). The use of peroxide vapor and a plasma generated by radio frequency energy releasing free radicals, ions, excited atoms, and excited molecules in a sterilising chamber has been patented (135). 

Ethylene oxide is able to inactivate all microorganisms. Bacterial spores are more resistant than vegetative cells, yeasts, and molds (287). Spores are 5 to 10 times more resistant than the vegetative cells (288). bacillus subtilis spores were the most resistant of those tested (289). Ethylene oxide was also shown to be vimcidal (290). 

Sterilization of Media First-order kinetics may be assumed for heat destruction of living matter, and this leads to a linear relationship when logarithm of the fraction surviving is plotted against time. However, nonlogarithmic kinetics of death are quite often found for bacterial spores. One model for such behavior assumes inactivation of spores via a sensitive intermediate state by the mechanism ... 

Bloomfield S.F. Arthur M. (1994) Mechanisms of inactivation and resistance of spores to chemical... 

Hoxey E.V., Soper C.J. Davies D.J.G. (1984) The effect of temperature and formaldehyde concentration on the inactivation of Bacillus stearothermophilus spores by LTSF. J Pharm... 

Pure Ti02 was recently reported to be active in the disinfection of water contaminated by spores of the type Fusarium solani [142], Bacillus anthracis [143], or Cryptosporidium parvum oocysts [144], or when supported as nanocomposites on zeolite H(i for E. coli deactivation [145], and it found applications in water treatment as a replacement for chlorine. Ag-Ti02 immobilized systems were used for inactivation of bacteria, coupling the visible light response of the system and the strong bactericidal effect of Ag [146]. Silver was deposited on hydroxyapatite to form nanocomposites with a high capacity for bacterial adsorption and inactivation [147], or used for airborne bacterial remediation in indoor air [148],... 

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