Saturday, March 15, 2008

PRINCIPALS OF STERILIZATION

An aura of mystery needlessly the art of sterilization. Modern pressure steam sterilizers function by simple application of ancient physical laws.

A sterilizer is a mechanical device for coagulating the protoplasm in microorganisms. The protoplasm of the microorganism dies and, of course, ceases to reproduce.

The protoplasm in microorganisms is very similar to the white of an egg or egg albumin. The coagulation of egg albumin is a coomon phenomena. We fry eggs and poach eggs almost daily.

When we fry an egg, the temperature reaches approximately 370 to 425 C in the pan.

When we poach an egg, due to the water in the pan, we never reach a temperature of more than 100 C.

In both instances we have coagulated the egg albumin,except, when poaching an egg we do it at a much lower temperature.

The only difference between the two methods of cooking the egg is that the fried egg is exposed to a dry heat the poached egg is exposed to a moist heat. We can assume then, that coagulation occurs at a lower temperature in the presence of moisture.

We know the different of microorganisms have varying resistance to unfavourable changes in their environment. This includes the degree of heat they can stand.

We know which organisme is the most resistant to destruction by heat. We know the conditions under which it is destroyed. We duplicate the destructive conditions in sterilizers, and therefore assume that all other organisms have been killed.

The most resistant pathogenic organism (one which is harmfull to man) is killed in hot air, after an exposure of one hour at 170 C. This same organism is killed at 134 C after only two minutes exposure in saturated steam.

Adapted from : atherton

0 comments: