As an expert sommelier and brewer, I can tell you that pumping a keg can indeed reduce foam, but it needs to be done carefully and in moderation. Let me explain why.
When you pump a keg, you are essentially increasing the pressure inside the keg, forcing the beer out through the tap. However, if you pump too much, the increased pressure can cause the beer to come out too quickly, resulting in a glass filled with pure foam. This is definitely not what we want when pouring a beer.
To avoid excessive foam, it's important to understand the right balance between pressure and flow rate. When you pump the keg, you are increasing the pressure, which can lead to faster pouring and more foam. On the other hand, if you don't pump at all, the pressure might not be enough to push the beer out smoothly, resulting in a slow and flat pour.
The key is to find the sweet spot where the pressure is sufficient to pour the beer smoothly but not so high that it causes excessive foaming. This sweet spot can vary depending on the specific keg and beer you are serving.
In my personal experience, I have found that a gentle and controlled pump before the first pour can help establish a good flow rate without creating too much foam. However, it's important to note that once you have achieved the right pressure, continuous pumping is usually not necessary for subsequent pours. In fact, excessive pumping between each pour can actually increase foaming.
Instead of relying solely on pumping, another technique to reduce foam is to tilt the glass at an angle while pouring. This allows the beer to slide down the side of the glass, minimizing agitation and reducing the formation of foam. Once the glass is about halfway full, you can then gradually straighten the glass and complete the pour.
Additionally, some keg pumps come equipped with a pressure relief valve. This valve allows you to release excess pressure before pouring, which can be particularly helpful if you accidentally pumped too much and are faced with a foamy situation. Simply open the valve briefly to release some air and then proceed with pouring.
To summarize, pumping a keg can reduce foam if done correctly and in moderation. It's important to find the right balance between pressure and flow rate to achieve a smooth pour without excessive foaming. Tilted glass pouring and pressure relief valves can also be useful techniques to minimize foam. Remember, practice makes perfect, and it may take some trial and error to find the optimal method for your specific keg and beer.