Off Flavors and Aromas
There are a number of predictable ways for your projects to go off the rails. By tasting and critically evaluating beer, you'll become comfortable in indentifying and diagnosing what caused certain tastes.
The flavors and aromas discussed in the following table are sometimes desirable. For instance, the sharp green apple flavor of acetaldehyde is a component of Budweiser. Buttery diacetyl provides complexity and sweetness to many British ales and traditional pilsners, but would be a flaw in a German hefeweizen.