Would you believe the drink above is lemonade, and the blue and purple colors are due to all natural ingredients? That’s right. The lemonade pictured is cooled with not-so-average ice cubes. These cubes are made from frozen butterfly pea flower tea.
Butterfly Pea flower tea is a popular non-caffeinated tea from Southeast Asia. It is made simply by steeping butterfly pea flowers in boiling water. Butterfly pea flowers get their deep blue hue from a natural compound called anthocyanin. This compound is the reason for the dark blue color of the ice cubes in the video above, and is also the reason for the amazing color change that occurs when the ice cubes come in contact with the acid from the lemon juice.
Anthocyanin undergoes reversible chemical changes (shown above) when exposed to either acids or bases. The chemical change alters the chemical structure, which alters the way it absorbs different wavelengths of light. When anthocyanin is exposed to a base, it reflects green and then yellow, depending on the strength of the base. When anthocyanin is exposed to acid, it turns purple and then red, depending on the strength of the acid. Because lemons are acidic, the melted butterfly tea ice cubes turn purple!
You can make this cool color changing drink at home with butterfly pea flowers and other normal household ingredients.
Making the butterfly pea flower ice cubes is simple. Just steep about 4 to 5 butterfly pea flower tea bags, or 25 to 30 dried pea flowers, in about 2.5 cups of boiling water. You can choose to leave the teabags/flowers steeping for up to 30 minutes for concentrated color, but just 10 minutes will get you blue ice cubes that can definitely give you a beautiful color change.
All that’s left is to make the lemon mix that will turn the ice cubes purple! Mix 1 cup of lemon juice with ¾ cups of sugar and stir until the sugar is completely dissolved. You can heat up the mixture a little to speed the mixing process.
Next, take your frozen butterfly pea flower tea and put it in the blender or food processor to create shaved ice. If your blender is like mine and can only make crushed ice pieces, that’s okay, just make sure there is some melted tea in your glass to get the immediate color change effect. Fill your glass halfway with crushed or shaved butterfly pea flower ice, and then add the lemon mix! As the anthocyanin comes in contact with the acid from the lemon juice, it will turn a pretty purple color. If you have some bigger crushed butterfly pea flower ice pieces, they will stay blue and only turn purple as they melt, which will create a swirly blue/purple gradient effect. Fill the glass with your desired amount of lemon mix (I fill it about ⅓ full) and top the rest of the glass with club soda! And viola, you have your color changing lemonade!
Citations
Kodippili, D. (2020). Color Changing Lemonade Slushie (Galaxy Lemonade). The Flavor Bender. www.theflavorbender.com/galaxy-color-changing-lemonade-slushie/
Kan, Viirj & Vargo, Emma & Machover, Noa & Ishii, Hiroshi & Pan, Serena & Chen, Weixuan & Kakehi, Yasuaki. (2016). Organic Primitives: Synthesis and Design of pH-Reactive Materials using Molecular I/O for Sensing, Actuation, and Interaction.