Some recipes start from an idea and just magically come together when the ingredients are in my hands. Others take years of fiddling, research, scrapping the whole idea and starting again, more fiddling, seeking expert advise, testing and retesting before satisfying results emerge. This recipe is definitely in the latter group. The idea of a color-changing recipe is one of those white whales I have been chasing for years, and finally, I have a dish I'm excited to share.
When I first read about color changing food pigments I could barely contain my glee. I mean, think of the possibilities: a dish that can change COLORS? It turns out that lots of plants have pigment molecules that are pH indicators. In a neutral or basic solution they will appear green-blue or blue-purple, but add some acid and they'll turn purple or red. (You've probably seen examples of this already: blueberries in blueberry pancakes will sometimes turn green if the batter has too much baking soda, or brush your teeth with a baking soda toothpaste after drinking a glass of red wine and you'll end up with a mouthful of blue foam.) Lots of dishes get a little something acidic thrown in at the end, so it didn't seem like making a dish to use this color-change trick would be too difficult.
My very first experiments quickly showed that I would need a mostly clear solution in order to show off the color change. (Opaque foods just muddied it up and got in the way). So I got to work trying out all sorts of ingredients with color-changing pigments: radicchio, red cabbage, blueberries. The findings of these tests were disappointing. Either the color would come out muddied and dull (blueberries) or the flavor would be horrid (red cabbage) or both (radicchio). And that's not even getting to the hardest part: acidity. Nearly everything that we eat is acidic. Egg whites and most tap water are slightly basic, but everything else is just varying degrees of acidity. For the color change to work, you need an acid addition that will significantly change the pH, but not until the dish is served. (So adding any acid to the mix beforehand is a no-go.) And this makes adding any flavor difficult. Just about every flavor-enhancing technique I thought of either muddied up the color or added acid. Perhaps, I thought, this is a phenomenon that works great in an eighth grade chemistry class, but really shouldn't be brought into the kitchen.
And then I met this little blue flower. (Hello, butterfly blue pea flower!) It doesn't seem to have much of an audience in the US yet, but Thai and Chinese cooks have long used this little flower to color foods and make teas with a brilliant blue hue. For my money, this is truly a remarkable ingredient. For one thing, it's hard to overstate how brilliant the color from this flower is. The pigment is highly soluble-- you don't even have to boil it to release the color. And since the flowers can be dried, it is easy to keep them on hand. The only slight detractor is that they don't have any real flavor on their own. But even that negative can be a boon-- you could use these little guys to color any sort of dish, and add whatever flavors you want separately. Finally I had an ideal candidate to make a color-changing recipe, and I decided a fancy cocktail would be just the thing to showcase this remarkable little ingredient. I chose to make an alcoholic beverage, but there is no reason that the same techniques wouldn't work for non-alcoholic beverages.