On Food and Cooking

Its active ingredient, stevioside, is available in
a purified powdered form. Neither it nor the
plant has been approved by the U.S. FDA as a
food additive, so they’re sold as dietary
supplements.
Intensive sweeteners often have some
flavor qualities that make them imperfect
replacements for table sugar. For example,
saccharin has a metallic aftertaste and can
seem bitter; stevioside has a woody after-
taste. Many are slower than table sugar to
trigger the sensation of sweetness, and their
taste persists longer after swallowing. The
relative sweetness of these sweeteners
actually goes down as their individual
concentration goes up, while combining them
produces a synergistic effect. So
manufacturers often use two or more to
minimize their odd qualities and maximize
their taste intensity.
Aspartame, a synthetic combination of two
amino acids, is the most widely used