How to Pour Culture Media: Steps and Best Practices
News 3 3 月, 2025
1. Temperature Adjustment
The ideal pouring temperature for culture media is around 45°C-50°C. A simple way to estimate this is by touching the bottle with both your palm and the back of your hand—if the palm doesn’t feel hot but the back of the hand does, the temperature is likely around 50°C. If the temperature is too high, condensation will form on the lid, and the solidification time will be longer. If too low, parts of the media may start solidifying before pouring.
2. Standing Time
After sterilization, the media should be kept in a water bath or incubator for temperature maintenance and used promptly. The standing time should not exceed 4 hours to prevent partial solidification.
3. Preparing the Plates
Before pouring, preheat the plates to 35°C-40°C. If surface inoculation is required, ensure the plates are free of condensation, as excess moisture may cause spreading colonies. Plates can be air-dried in a sterile laminar flow hood but should not be overdried to avoid cracking during incubation.
4. Pouring Volume & Mixing
The recommended pouring volume is 18-20mL per plate. If incubation exceeds 48 hours or the temperature is above 40°C, increase the volume to 25mL to prevent excessive evaporation and cracking. Pour the media gently along the plate wall to minimize bubbles. If bubbles appear, gently tilt the plate to move them to the edge. If mixing is needed, gently swirl the plate 5-15 times to ensure even distribution of inoculated material.
5. Avoiding Contamination
To prevent contamination:
- Loosen media-containing bottles before sterilization.
- Heat the media in a boiling water bath or steam bath to dissolve but avoid overheating.
- Prepare one extra sterilized plate to serve as a blank control.
6. Incubation
Once poured, plates should be allowed to cool and solidify before incubation. To minimize condensation:
- Leave plates open for 5 minutes in a sterile hood before closing and inverting them.
- Alternatively, stack plates in an inverted position while cooling before incubation.
Proper pouring techniques help ensure accurate microbial testing and reliable experimental results.