How much media is weighed for SCDA, and what is its pH? Why is pH measured before and after sterilization?

Media Weight
Typically, 40 g of SCDA powder is dissolved in 1 liter of distilled water.

pH
The pH should be 7.3 ± 0.2 at below 25°C after and before sterilization.
pH is measured before sterilization to ensure the media is properly prepared, and after sterilization to confirm the media’s suitability for use in culturing microorganisms.

Sterilization can lead to the formation or breakdown of certain compounds (like carbohydrates or peptides) that can either release hydrogen ions (H⁺) or hydroxide ions (OH⁻), thus changing the pH.

Buffers in the media may lose their effectiveness or undergo changes during sterilization, altering the pH.
The high temperature and pressure during autoclaving can break down some components of the media, such as proteins or sugars, which may release acidic or basic by-products, causing the pH to shift slightly.