cooking water or sprinkled on the food can help with both aims: its citric acid binds up metal ions Cooking red cabbage with acidic apples or vinegar keeps it from turning purple; dispersing baking soda evenly in batters, and using as little as possible to keep the batter slightly acidic, will keep blueberries from turning green Creating Color from Tannins On rare and wonderful occasions, cooking can actually create anthocyanins: in fact, it transforms touch into color! Colorless quince slices cooked in a sugar syrup lose their astringency and develop a ruby-like color and translucency Quinces and certain varieties of pear are especially rich in phenolic chemicals, including aggregates (proanthocyanidins) of from to 20 anthocyanin-like subunits The aggregates are the right size to cross-link and coagulate proteins, so they feel astringent in our mouth When these fruits are cooked for a long time, the combination of heat and acidity causes the subunits to break off one by one; and then oxygen from the air reacts with the subunits to form true anthocyanins: so the tannic, pale fruits become more gentle-tasting and anything from pale pink to deep red (Interestingly, the similar development of pinkness in canned pears is considered discoloration It’s accentuated by tin in unenameled cans.) Turning Red Wine into White The sensitivity of anthocyanin pigments to pH is the basis for a remarkable recipe in the late Roman collection attributed to Apicius: To make white wine out of red wine Put bean-meal or three egg whites into the flask and stir for a very long time The next day the wine will be white The ashes of white grape vines have the same effect ...long time, the combination of heat and acidity causes the subunits to break off one by one; and then oxygen from the air reacts with the subunits to form true anthocyanins: so the tannic, pale fruits become more gentle-tasting... Put bean-meal or three egg whites into the flask and stir for a very long time The next day the wine will be white The ashes of white grape vines have the same effect ... Turning Red Wine into White The sensitivity of anthocyanin pigments to pH is the basis for a remarkable recipe in the late Roman collection attributed to Apicius: To make white wine out of red wine Put bean-meal or three egg whites into the