What fermentation-derived flavor commonly appears in ales but not lagers?

Ales are fermented with top-fermenting yeast, typically Saccharomyces cerevisiae, which operates at warmer temperatures and allows for the development of a wider range of flavors and aromas. One prominent trait that characterizes many ales is their fruity esters, which can include notes of bananas, apples, and other fruits. These esters are a result of the yeast's metabolic processes during fermentation, particularly at the warmer temperatures used for ales.

In contrast, lagers are brewed with bottom-fermenting yeast (Saccharomyces pastorianus) at cooler temperatures. This process tends to produce a cleaner, crisper profile with fewer fruity esters, leading to minimal fruity flavors in the finished product. As such, while ales showcase a variety of fermentation-derived flavors, the fruity characteristics are a hallmark of ales and a distinguishing feature that sets them apart from lagers.