Dry heat sterilization is the use of high temperatures to sterilize microorganisms by coagulating and denaturing the proteins in their cells. It is used to (1) sterilize (2) ensure that equipment, etc., is not contaminated.

Operation method

dry-heat sterilization

Principle

Dry heat sterilization is the use of high temperature to make the microbial cell protein coagulation denaturation and achieve the purpose of sterilization. Protein coagulation in the cell is related to its own water content, in the heat of the bacteria, when the environment and the greater the water content in the cell, the protein coagulation faster, and vice versa, the smaller the water content, slow coagulation. Therefore, compared with moist heat sterilization, dry heat sterilization requires high temperature (160-170 ℃), long time (1-2 hours). But dry heat sterilization temperature can not exceed 180 ℃, otherwise, the paper or cotton plugs will be wrapped utensils scorched, or even cause combustion. The structure of the electric oven used for dry heat sterilization is shown in Figure VI-3.

Materials and Instruments

Petri dishes Test tubes Straws
Distilled water
Petri dish, test tube, straw, electric oven

Move

I. Loading items to be sterilized Put the packaged items to be sterilized (petri dishes, test tubes, pipettes, etc.) into the electric oven, the items should not be placed too crowded, so as not to impede the flow of hot air. At the same time, the sterilized items should not be in contact with the iron plate on the inner wall of the electric oven to prevent the wrapping paper from burning and catching fire. 

II. Warming up Close the door of the electric oven, plug in the power plug, toggle the switch, rotate the thermostat regulator to the red light, so that the temperature gradually rise. If the red light is off, the green light is on, it means that the box has stopped heating, at this time, if it has not reached the required temperature of 160-170 ℃, it is necessary to rotate the regulator so that the red light is on again, and so on repeatedly adjusted until it reaches the required temperature.

III. Constant temperature When the temperature rises to 160-170°C, it is maintained at this temperature for 2 hours by automatic control of the thermostat. IV. Cooling Disconnect the power and cool down naturally.

V. Unpacking and retrieval When the temperature inside the electric oven drops below 70°C, open the door and remove the sterilized items.

Caveat

1. Do not open the door of the electric oven before the temperature inside the oven drops to 70℃ to avoid the glassware blowing up.

2. Wait for the temperature to rise to a certain height before timing.

Common Problems

The coagulability of proteins in the cell is related to its own water content, when the bacterium is heated, when the environment and the water content in the cell is greater, then the protein coagulation will be faster, and vice versa, the smaller the water content, the coagulation is slow.

For more product details, please visit Aladdin Scientific website.

https://www.aladdinsci.com/