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So there I was, ready with a tea bag in one hand, a slice of lemon in the other and a couple of grandkids collared into being the audience. I said we were going to do a chemical experiment. They were not too excited. After all, they had seen tea being made before.
I think they assumed we were going to talk about, ho-hum, why tea becomes a lighter colour when lemon juice is added. Indeed, it does, because fermentation of tea leaves produces thearubigins, complex molecules in the polyphenol family with a nearly black colour. Addition of an acid like lemon juice makes a slight alteration in their molecular structure, resulting in a change in the wavelengths of light absorbed and reflected. The tea turns a lighter colour. But the kids were in for a surprise.
When I dunked the teabag in the hot water, the brew became a brilliant blue! Now there was an 鈥渙ooh,鈥� further amplified when a squeeze of lemon turned the tea into a crimson purple colour! And there was more amazement when the addition of baking soda, a base, first changed the colour back to blue, then to green! This obviously was no ordinary tea. It wasn鈥檛. This was butterfly pea tea.
Butterfly pea is a plant found mostly in Southeast Asia that produces flowers with beautiful blue petals in the shape of a butterfly. It also produces pods with seeds that land it in the legume family, thus the term 鈥減ea.鈥� Its botanical name, Clitoria ternatea, is also intriguing. It seems that during the 17th century, some botanist with an active imagination saw the flower as resembling a particular part of the female anatomy.
The blue colour of butterfly pea flowers is due to delphinidin, one of many anthocyanins responsible for the colour of flowers, berries, fruits, vegetables and even red wine. Anthocyanins have antioxidant properties, meaning they can neutralize potentially tissue-damaging free radicals that are byproducts of the reaction between oxygen and glucose that cells use to generate energy. It may explain why butterfly pea flowers have a history as a medicinal herb in Asia.
Hot water extracts delphinidin from the petals, hence the blue tea. But there are actually four slightly different forms of delphinidin that can change back and forth depending on the acidity, the pH, of the solution. With increased acidity, a purple colour dominates, but a basic solution results in a greenish hue. I could have used purple cabbage to carry out the experiment because cyanidin, the anthocyanin it contains, also exhibits colour changes as the pH is varied. However, I had a reason for choosing butterfly pea.
Recently the use of artificial dyes in food has been much criticized, especially by Robert F. Kennedy Jr., who inexplicably has been installed as the Human Health and Resources Secretary in the U.S. despite having no scientific qualification for the position. He likes to vilify artificial dyes by referring to them as 鈥減etroleum-based,鈥� creating an image of some sort of oily crud that nobody would want in their food. Artificial dyes are far removed from petroleum, having undergone numerous chemical reactions to arrive at their final form. In any case, the safety of a substance does not depend on its ancestry; it is determined by studies that have been carried out. for which there is no evidence, is made from petroleum. The starting material for the synthesis of vitamin A, which Kennedy erroneously believes can prevent measles, is beta-ionone. Guess where the compounds to produce this chemical come from.
As I have said many times, while the evidence that artificial dyes produce adverse effects is paper thin, I am not opposed to their removal because they serve only a cosmetic purpose and . But replacing the artificial dyes with natural ones does not make Froot Loops or Skittles healthier. Nevertheless, there is a movement toward the use of natural dyes. Extracts of beetroot or the cochineal insect yield red, safflower or turmeric can produce yellow, and spinach powder supplies green. However, a blue colour that is comparable to synthetic blue has been elusive. Enter butterfly pea blue! Although not as brilliant as synthetic Brilliant Blue FCF (for colouring food) it has found a use in sports drinks, alcoholic beverages, candies, ice cream and yogurt.
Recently, the St. Louis-based sought and received approval for using butterfly pea flower extract in cereals, crackers, corn and potato chips. I don鈥檛 know why one would want to colour potato chips blue, except perhaps to give the impression that they are made from blue or purple potatoes that really do exist and derive their colour from natural anthocyanins.
Maybe the most imaginative use of butterfly pea flower extract is in the production of . Actually, the beverage contains no indigo but owes its blue colour to butterfly pea blossoms and its flavour to various botanicals in addition to the traditional juniper berries. The gin commemorates the opening of the famed Empress Hotel in Victoria, B.C., in 1908, hence the name. The hotel is majestic with an old-world atmosphere and is known for its spectacular afternoon tea service that I experienced, although I don鈥檛 remember any gin. The appeal of Empress 1908 is that when mixed with tonic water, it changes colour to an alluring pink.
Tonic water first appeared in India during the early 19th century, served to British soldiers with the aim of preventing malaria. It contained quinine, extracted from the bark of the Peruvian cinchona tree, that at the time was used to treat malaria and there was hope it could also prevent the disease. Because quinine is very bitter, sugar and carbon dioxide were added to make for a more palatable tonic.
Today鈥檚 tonic water contains only a trace of quinine and has citric acid added for flavour. This acid and the carbonic acid that forms on carbonation make tonic water acidic. Presto! An intriguing colour change when it is added to Empress 1908 gin. A fun demonstration, but more appropriate for adults than grandkids. Anyway, the butterfly pea tea experiment turned out to be more than ho-hum, especially when we made ice cubes from the tea and added them to acidic lemonade. Soon the blue ice cubes were floating in a pretty pink solution. And there was a happy ending to this chemistry lesson. The product of the reaction could be consumed.
