Good quality Brussels sprouts should be bright green, without yellowing or discoloration, and have a firm texture. The butt end may be slightly discolored, but should not be dark. Brussels sprouts should be sweet and mild in flavor when cooked. Bitterness varies among cultivars and is associated with high concentrations of specific glucosinolates (sinigrin and progoitrin). Bitterness can also be induced by storage conditions.