Green Blueberries and Blue Walnuts

Appears in
On Food and Cooking

By Harold McGee

Published 2004

  • About

Sometimes the solid ingredients folded into bread and muffin batters turn disconcerting colors: blueberries, carrots, and sunflower seeds may go green, and walnuts blue. This happens when the mix contains too much baking soda, or when the soda isn’t evenly mixed in the batter, so that there are concentrated alkaline pockets. Because the anthocyanin and related pigments in fruits, vegetables, and nuts are sensitive to pH, and their normal surroundings are acidic, alkaline batters cause their colors to change. Small brown spots on the surface of the finished bread or muffin are also a sign of incomplete mixing; the browning reactions proceed faster in more alkaline portions of the batter.