Why does beer have too much gas?

Sometimes when we open a beer, it erupts in a volcano of foam. What can cause this over‑carbonation? Beer needs to have the correct volume of gas; both excess and lack of CO2 can keep us from fully enjoying our favorite drink, since the final result differs from what the brewer intended.

At homebrew level, the most common cause is usually too much sugar when doing the priming. When we carry out a second fermentation in the bottle, if we add too much sugar, we will cause over‑carbonation in the beer. The yeast will turn this sugar into CO2. It is important to always measure the sugar we add precisely. Professional brewers often choose to carry out this second fermentation with a portion of green wort instead of sugar.

In other cases, when we opt for forced carbonation and inject CO2 into the beer artificially, it is also possible that we fail to control the pressure properly or that the regulator does not show the correct value due to malfunction or poor configuration.

Another common cause of over-carbonation is bottling too early. We must wait for fermentation to finish before packaging the beer. Sometimes there are lulls in yeast activity, and we mistakenly believe fermentation has ended. The risk is that there are still fermentable sugars left unprocessed and that fermentation will resume uncontrollably in the sealed container.

It could also be that the beer is contaminated. It may happen that some bacteria or fungus entered the beer during fermentation or bottling and consequently consumed the available sugars, generating not only excess gas but also unpleasant odors and flavors. This is easy to detect, as the beer’s profile is not only unappealing but also does not match the character of its style. This type of contamination can be reminiscent of vinegar due to its acidity. To avoid it, it is vital to constantly check the hygiene of our equipment and containers.

However, contamination can also be present in the raw materials. If we use old malts, they may be damp and therefore moldy. It’s especially important to be careful with yeast. Using old yeast is risky, as it can lead to a slow fermentation because it hasn’t had time to wake up from dormancy, but then it may develop a vigorous fermentation in the keg or bottle. This is known as a late fermentation. That’s why whenever we use old yeast, we must prepare a starter to activate it and avoid unpleasant surprises.

In conclusion, to ensure proper carbonation we must be thorough with priming or forced carbonation, wait until fermentation has finished, and thoroughly clean both the equipment and the ingredients. With these tips you’ll achieve beer with the perfect level of carbonation.