Home brewing: Degassing techniques

Dissolved gases, such as CO₂, can interfere with measurements, leading to inaccuracies. In devices like EasyDens, for example, bubbles in the measuring cell can compromise the accuracy of the results. Degassing is therefore a crucial step in preparing liquid samples for accurate measurement, especially when it comes to applications like home brewing or laboratory analysis.

But which technique should you use? Choosing the most suitable method will depend on factors such as sample volume, time constraints, available equipment, and the need for precision. Below are four examples of degassing techniques for samples – stirring, shaking, syringe, and sonication – with clear instructions and key considerations included for each. 

Agitating a liquid by stirring it is one of the simplest ways to remove dissolved gases from a sample. 

Process: 

• Stir the sample continuously until bubbling stops (up to 15 min). When working with multiple samples, using a magnetic stirrer can save time and effort while ensuring consistent results across batches.

NOTE: Ensure the sample is covered during stirring to prevent evaporation, particularly for liquids that contain alcohol.

Shaking is one of the most convenient and commonly used degassing techniques, especially for home brewing.

Process:

• Pour the sample into a sealed container (e.g. an Erlenmeyer flask with a rubber stopper or a clean PET bottle).
• Shake the container thoroughly and then release the pressure by lifting the stopper or unscrewing the bottle cap.
• Repeat this process until the pressure stops building up and bubbling has completely stopped.

NOTE: For samples containing particles larger than 1 mm, make sure you filter the sample before measurement to ensure accuracy.

A syringe provides an efficient and controlled method to degas liquid samples.

Process:

• Fill the syringe with the sample until it is two-thirds full.
• Seal the tip with your finger and pull back the plunger to create a vacuum.
• Release your finger to let the CO₂ escape and push the plunger forward to expel any remaining air.
• Repeat these steps several times to ensure complete degassing.

NOTE: Use a syringe large enough to allow adequate space for creating a vacuum.
 

Sonication, or the use of an ultrasonic bath, is another reliable degassing technique.

Process:

• Place the sample in an ultrasonic bath and sonicate for 5 min to 10 min. The sample container should be covered during the process to prevent the evaporation of volatile components (e.g. alcohol).

NOTE: Ensure the bath is set to the appropriate time and intensity to avoid damaging the sample.