Sure, a few innovative brewers have managed to successfully pull off the odd cucumber Pils or sweet potato porter, but such examples are rare, and even well-done veggie beer typically features the produce aisle in only a supporting role.
Occasionally, though, you may find that a beer tastes plant-like even when you’ve stuck to only Reinheitsgebot-approved ingredients. In these cases, the issue is likely more one of process than it is of produce. Here, then, are a few common culprits and some suggestions to solve them.
Dimethyl sulfide (DMS) is usually described as having an aroma and flavor reminiscent of canned corn, but some individuals perceive it as cooked vegetables, especially cabbage, onions, or celery. DMS arises naturally as part of the malting process, but the heat of kilning usually eliminates this volatile compound. However, in very light malts, especially Pilsner varieties, the duration or intensity of kilning can be insufficient to fully drive DMS away. In wort prepared with a large proportion of Pilsner malt, an extended boil of 90 minutes or more is recommended.