MOIST HEAT

This involved the used of moisture to achieved sterilization goals. Sterilization and disinfection where employed with this method. This method is more dependable and simple to control compare to others method of sterilization, the method is mostly used worldwide. Destruction of bacteria using this technique depend on the amount of heat apply, if accurate amount of heat is apply, their will be total destruction of all microbial life. This technique used steam pressure under certain condition and seems to be the older method which is still in used till date. But things to observed in applying these method of sterilization, is to understand the purpose for differentiation between and set in limitation of the technique, because the way which they kill microorganism is not the same. When heat moisture that is under pressure is used the rate at which the organism are been killed and destroyed by not reversing the process of denaturizing their enzyme and protein. The process is achieved under these certain condition depend on the viability of the amount of temperature and water present e.g egg albumin will coagulate at 56ºC with water of 50%.

Egg albumin will coagulates at 74-80ºC with water 25%  and egg albumin will coagulates at 160-170ºC without water, on the above chart it show water in these technique foster the rate of reaction that take place in the system. In these dry process the change in the moisture concentration as a factor which considers the killing process of the organism in question to be the oxidation of the cell concentration.

The sterilization of a heat need a higher temperature and long time exposure compound to that of moisture heat take for example when heat is applied to water at sea level their be an increase in temperature it get to 100ºC at these point, any addition amount of heat introduce will increase the amount of energy the sea in such result to evaporation with increase or decrease the amount of temperature present in the sea, where by the water start boiling. It should be born in mind that water dose not exceed 100ºC, the rate at which water boil depend on it atmospheric pressure. At a high attitude water has a reduce atmospheric pressure in such case water at attitude boil at temperature lesser than 100 ºC. The killing of micro organism is less effective in these attitude, on the other hand when the atmospheric pressure is increased, the rate of temperature required to boil the water also increase, in these phenomenon it is more effective in killing micro organism. These are the technique applied in the use of autoclave for sterilization.

The rate at which boiling water kill micro organism at 100 ºC will kill non sporing micro organism for 10 minute, but spore organism resist this time except the time is increase to 30 minute before they can be kill. At sometime a categories group of spore resist these time except they are boil up to one hour before they could be killed at the same temperature. But when these occur, the addition of 2% sodium carbonate is recommended because the substance has bactericidal effect at boiling water and it will kill the micro organism in 30 minute. The technique is suitable for infected instrument such as animal autopsy that is required urgently for particular purpose but the effect is that sodium carbonate curse rusting of the instrument. It advisable the instrument is stored in an aseptic condition.

Using of steam at 100 ºC, it main purpose is for sterilization of complex median, that may lead to hydrolysis of their constituent at a high temperature, e.g. gelatin and sugar etc. these material are sterilized by using a special instrument called tyndallisation. On using this instrument the sterilization is achieved for three days. On the first day the medium is seamed for 30 minute, this first day kill non sporing organism, after that the medium is incubated at room temperature over night. On the second day the medium is steamed for 30 minute to kill the organism that growth spore for the first day over night incubation. On the third day it also steam for 30 minute again. The third steaming kills the remaining spore after the first and the second incubation. The repeat steaming and incubation is done in other to be sure that the medium is properly sterilized, with the repeated steaming and incubation aid the growth of the remaining organism in the medium which will be killed in the next steam. Tyndallisation is necessary when medium are to be sterilized in a favorable condition. Also this method of sterilization may not kill anaerobic organism spore barrier, until the incubation of the organism is carried out anaerobically before sterilization using this method can be achieved.