Isoamyl Acetate
Isoamyl acetate is a flaw that manifests as banana, circus peanut, or pear candy aromas. In a German-style hefeweizen this may be all well and good, but in other beer styles, wine, and many spirits, the presence of prominent banana notes are generally seen as a fault. The cause is usually fermentation temperature or yeast health and in spirits possibly the width of the cut off the stll.