Faster fermentation is generally not better for the majority of beer styles. While it may seem convenient to have a quick turnaround time, the quality of the final product can be compromised when fermentation occurs at a high temperature and at a rapid pace.
One of the main concerns with fast fermentation is the production of off flavors. When yeast ferment at higher temperatures, they can produce higher levels of fusel alcohols, which are higher alcohols that can contribute to a harsh and solvent-like taste. These fusel alcohols are typically undesirable in most beer styles and can give the beer a hot or boozy character.
Additionally, fast fermentation can lead to the production of excessive esters and phenols. Esters are fruity and floral compounds produced by the yeast during fermentation, and phenols can give off flavors such as clove or medicinal notes. While these compounds can be desired in certain beer styles like Belgian ales or wheat beers, they can be overpowering and unpleasant in others.
In my own brewing experiences, I have found that slower and cooler fermentation tends to produce better results. I have noticed that when I ferment my beers at lower temperatures, the yeast activity is more controlled, resulting in a cleaner and more balanced flavor profile. The slower fermentation also allows for the yeast to fully attenuate, meaning they consume more of the fermentable sugars and produce a drier beer.
Cool and fast fermentation would be ideal, as lower temperatures can help to suppress the production of off flavors. However, yeast activity tends to slow down significantly at lower temperatures, so it can be difficult to achieve a fast fermentation while keeping the temperature low. This is why many brewers opt for a slower and cooler fermentation process to ensure the best quality beer.
To summarize, while faster fermentation may seem appealing for its quick turnaround time, it can lead to off flavors and a less desirable final product. Slow and cool fermentation is generally the preferred method to produce high-quality beer with balanced flavors.