As both a sommelier and a brewer, I can offer some insights into the process of bottling homebrew and whether stirring the beer before bottling is necessary or beneficial. In my experience, it is generally not recommended to stir the beer just before bottling for a few reasons.
Firstly, when you stir the beer, you introduce oxygen to the liquid. Oxygen is the enemy of beer, especially at this stage of the brewing process. Oxidation can cause off-flavors and stale aromas in the beer, which can negatively impact its overall quality. Therefore, it is crucial to minimize contact with air as much as possible during bottling to preserve the freshness and taste of the beer.
Secondly, stirring the beer just before bottling can disturb the sediment that has settled at the bottom of the fermenter. This sediment, also known as trub, consists of spent yeast, hop particles, and other solids. Allowing the trub to settle before bottling helps to clarify the beer and prevent unwanted flavors or cloudiness in the final product. By stirring the beer, you risk reintroducing these particles into the liquid, which can affect both the appearance and taste of the beer.
Furthermore, stirring the beer can also disrupt the carbonation process. When bottling homebrew, you typically add priming sugar or carbonation drops to induce a secondary fermentation in the bottle. This fermentation produces carbon dioxide, which is trapped in the sealed bottle, creating natural carbonation. If you stir the beer vigorously before bottling, you may release some of the dissolved carbon dioxide, resulting in undercarbonated or flat beer.
That being said, there may be some rare cases where stirring the beer before bottling could be beneficial. For example, if you have added additional ingredients such as fruit puree or spices during secondary fermentation, gently stirring the beer can help ensure even distribution of these flavors. However, this should be done with caution and only if necessary, as the potential risks of oxygen exposure and disturbing sediment still apply.
Stirring your homebrew just before bottling is generally not recommended. It can introduce oxygen, disturb sediment, and interfere with the desired carbonation levels. Instead, focus on careful handling and transferring techniques to minimize oxygen contact and maintain the clarity and quality of your beer.