On Food and Cooking

300 known anthocyanins, and a given fruit or
vegetable will usually contain a mixture of a
dozen or more. Like many other phenolic
compounds, they are valuable antioxidants (p.
255).
Anthocyanins and anthoxanthins reside in
the storage vacuole of plant cells, and readily
bleed into surrounding tissues and ingredients
when cell structures are damaged by cooking.
This is why the lovely color of purple-tinted
asparagus, beans, and other vegetables often
disappears with cooking: the pigment is stored
in just the outer layers of cells, and gets
diluted to invisibility when the cooked cells
break open. The main function of the
anthocyanins is to provide signaling colors in
flowers and fruits, though they may have
begun their career as light-absorbing
protection for the photosynthetic systems in
young leaves (see box, p. 271). Anthocyanins
are very sensitive to the acid-alkaline balance
of foods — alkalinity shifts their color to the