Micro-organisms destruction

The minimum F value is based only on microbial spore destruction. It is believed that F0 = 12 min is a realistic minimum value, since most mesophilic spore-forming micro-organisms have D values <0.5 min at 121°C. Even if Dm = 1.0 min, the spore log reduction value according to Eq. (10) would be 12. ... 

G. Metabolic Difference. Micro-organisms attack wood by secreting enzymes into the immediate structure which in turn break down the wood components into small, soluble units that become nutrients for the organism. The main destructive enzyme system the wood-rotters contain is a class of proteins known as cellulases. These enzymes break down he polymeric cellulose, the strong backbone of wood, into digestible units. Humans do not possess this enzyme system consequently, we cannot degrade cellulose-containing materials. 

It may be necessary to differentiate between antemortem and postmortem production of alcohol in a decomposed body. Little information can be obtained from the analysis of only a single sample of blood. Samples should be taken from several different sites, as well as from the right and left chambers of the heart. These samples should each be divided into two parts, one portion being stored without a preservative and the other preserved with 1% sodium fluoride. If the unpreserved and preserved samples contain different concentrations of alcohol, this is due to the continued destruction or production of alcohol by micro-organisms in the blood. If the results of the analyses are the same, then the decomposition or production of alcohol has either not occurred or has ceased. 

Mixed populations of common brewery contaminants, in beer subjected to a range of temperatures of various times, were examined for viability (Fig. 20.22). Typically with temperatures over 50 C (122°F) an increase in temperature of TC (12 6°F) accelerated the rate of cell-kill ten-fold. Thus at 60°C (140°F) the minimum time required for the population to be killed may be 5 6 min, but at 53°C (127 4°F) it would be 56 min and at 67°C (152-6 F) would be 0 56 min. One Pasteurization Unit (PU) has been defined arbitrarily for the beer as the biological destruction obtained by the holding of a beer for one minute at 60°C (140 F). The effect is a product of (/) the lethal rate (djc/d/, where x is the number of viable micro-organisms per wort volume and t is time in min) and (//) the time of application. Thus PU/min = 139 where a is the temperature (in °C) minus 60°C. Pasteurization Units have been shown to be additive in their effects in a complex treatment where temperature... 

Cleaning and disinfection. The procedures for cleaning and disinfection (destruction of micro-organisms - but not necessarily spores - by chemical agents, see Sect. 

Disinfection, sanitisation, decontamination, chemical sterilisation, are only a few terms for these processes. Disinfection, defined as removal, destruction or de-activation of micro-organisms on objects or surfaces, is the term of preference in this book. 

Mechanical removal (along with destructive effect of heat) of micro-organisms, however this is not a sterilising cycle... 

In the food industry the inter-relationship between micro-organism growth, temperature and time is of vital importance. For the destruction of micro-organisms and the inactivation of enzymes, heat treatment may well be selected. Other possibilities include chemicals and ionising radiation. 

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