anthocyanins are stored are generally acid,
while the rest of the cell fluids are less so.
Cooking water is often somewhat alkaline,
and quick breads include distinctly alkaline
baking soda. In acid conditions, anthocyanins
tend toward the red; around neutral pH,
they’re colorless or light violet; and in
alkaline conditions, bluish. And pale
anthoxanthins become more deeply yellow as
alkalinity rises. So red fruits and vegetables
can fade and even turn blue when cooked,
while pale yellow ones darken. And traces of
metals in the cooking liquid can generate very
peculiar colors: some anthocyanins and
anthoxanthins form grayish, green, blue, red,
or brown complexes with iron, aluminum, and
tin.
The Aid: Acids The key to maintaining natural
anthocyanin coloration is to keep fruits and
vegetables sufficiently acidic, and avoid
supplying trace metals. Lemon juice in the