
Grapefruit bitters are concentrated cocktail bitters made from grapefruit peel, herbs and roots.
Bitterness and citrus oil are separable, and only the oil is specific: a dash of another citrus bitters plus grapefruit peel expressed over the finished drink gets both back. Peel alone is aroma without bitterness, which some drinks prefer.
Orange peel in front instead of grapefruit, and both are citrus bitters at the same dash strength. In most builds they swap dash for dash; where the drink was leaning on grapefruit’s harder, drier bitterness, orange leaves it rounder and sweeter-seeming.
Grapefruit character rests on trace sulfur compounds present in vanishingly small amounts, and they are the first thing to go. Everything else about the bottle is stable at 40–45%. Expect it to read as generic citrus bitters within a year of opening.