By Sophia Attard, 15
CAGIS Member
Looking for a way to stay cool this summer? Try out this tasty recipe for colour-changing slush lemonade and explore some exciting food chemistry along the way!
You Will Need:
- Water (7-8 cups)
- ½ cup lemon juice (about 3-4 lemons)
- 1 cup brown sugar
- 2 cups of soda water
- 1-2 tbsp fresh or dried butterfly pea flowers (or 2-3 bags of butterfly pea flower tea). Either can be ordered online or found in specialty tea shops.
Makes 6-8 servings of slush lemonade.
Instructions
HEAT CAUTION: parent/guardian supervision required.
Make the Simple Syrup
- Add 1 cup of boiling water to 1 cup of brown sugar in a large mixing bowl.
- Stir until the sugar is dissolved
- Let the mixture cool on the counter and save for the next day.
Make the Butterfly Pea Flower Tea
- Boil another 3 cups of water and add it to either a teapot or a stovetop pot.
- Place the flowers or tea bags in the boiled water.
- Let it sit for around 5 minutes.
- Remove the tea bags or strain the flowers.
- Cool in the fridge for about 15 minutes, or until no longer warm.
Make the Ice Cubes
- Pour cooled tea into an ice cube tray. Be sure that the water is no longer warm if using plastic ice cube trays.
- Also fill a second ice cube tray with plain water.
- Let them both freeze overnight.
- Place the butterfly pea ice cubes and regular ice cubes in a food processor or blender. Alternatively, you can place the cubes in a freezer bag and crush using a rolling pin or mallet.
- Crush the ice into chunks (we don’t want it to be too fine; smaller chunks are best).
Slushie Assembly
- Split the crushed ice between the desired number of servable cups (6-8).
- Split the sugar syrup between each cup (about 2-3 tbsp per cup for 6-8 servings).
- Slowly pour in ¼ cup of soda water per cup.
- Split the lemon juice between each cup (about 1 tbsp per cup) and watch the colour change!
- Taste and top up with soda water as needed.
What’s Happening?
Chemist, Dr. Sydney Brooks, explains that butterfly pea flowers contain natural pigments called anthocyanins, which are pH indicators. A pH indicator is a substance that changes colour depending on how acidic or basic its surroundings are. This makes butterfly pea flowers useful for demonstrating changes in pH.
When the butterfly pea tea is mixed with the lemonade, the citric acid in the lemon juice lowers the pH of the mixture. This is what makes the colour change from blue to purple, pink, or magenta as more lemon juice is added.
The colour change therefore gives us a visible way to observe a change in pH without needing special equipment to measure it!
This article was inspired by Karen Cardona’s colour-changing lemonade CAGIS Virtual event, which taught us the secret to making colour changing lemonade (similar to our recipe)!
About the Author: Sophia is a CAGIS Teen Ambassador and grade 11 student with a wide variety of interests, from STEM to drama to business. Outside of school, she works as a lifeguard and swim instructor and enjoys volunteering, where she values helping others in any way possible.
