Which of the following is primarily a yeast-derived flavor?

The flavor primarily derived from yeast is associated with certain esters and phenols produced during fermentation. Yeast, especially the specific strains used in brewing, can create a range of flavors, and among those, fruity esters are common, with apple being a notable example. When yeast ferments sugars in the wort, it can produce compounds such as isoamyl acetate, which is known for its banana and apple-like aromas. This is why apple is recognized as a flavor that is primarily yeast-derived.

In contrast, vanilla typically comes from vanilla beans or may be artificially produced, caramel flavors often stem from the Maillard reaction during malting or from caramelization of sugars, and citrus flavors are generally derived from hops or adjuncts rather than the yeast itself. Understanding these distinctions is crucial for recognizing how different flavors originate in brewing and fermentation processes.