The white stuff in beer is known as sediment, and it can come from a couple of different sources. Sediment is essentially made up of yeast and protein particles that are present in the beer.
One possible reason for sediment in beer is when a brewery chooses not to filter or pasteurize their beer before packaging it. Filtering and pasteurization are methods used to remove any solids or microorganisms from the beer, resulting in a clearer and more stable product. However, some breweries may opt not to filter or pasteurize their beer, either for flavor reasons or to retain certain characteristics of the beer. This can result in sediment being present in the final product.
Another way sediment can end up in beer is through a process called bottle conditioning. Bottle conditioning is a traditional method of carbonation where additional yeast and sugar are added to the beer before it is bottled. The yeast consumes the added sugar, producing carbon dioxide, which naturally carbonates the beer. During this process, some yeast particles can settle at the bottom of the bottle, creating sediment. This is more commonly seen in craft beers and traditional beer styles.
I personally find sediment in beer to be quite fascinating. It adds a certain rustic and natural character to the beer, and can often be a sign of a beer that has undergone minimal processing or is bottle conditioned. When pouring a beer with sediment, it is important to handle the bottle carefully and leave the sediment behind in the bottle, so you can enjoy a clear pour.
In some cases, the presence of sediment can also affect the flavor and mouthfeel of the beer. The yeast and protein particles can contribute to a slightly thicker or creamier texture, and can also add a subtle earthy or yeasty flavor. This can be particularly noticeable in certain styles of beer, such as Belgian ales or hefeweizens, where yeast is intentionally left in the beer for added complexity.
To summarize, the white stuff in beer is sediment, which consists of yeast and protein particles. It can be present in beer when a brewery chooses not to filter or pasteurize their beer, or when a beer is bottle conditioned. Sediment can contribute to the overall character and flavor of the beer, and is often seen as a desirable attribute in certain beer styles.