Popping candy is made by heating the sugars sucrose, lactose and corn syrup (plus some flavouring) to boiling point. Carbon dioxide (CO2) is bubbled through the molten mixture at a pressure of around 600 pounds per square inch (psi) – several times the pressure in a champagne bottle. The mixture is then cooled rapidly under pressure to prevent the gas from escaping as the candy solidifies.
When the pressure is released, the candy shatters into smaller pieces, each containing tiny bubbles of CO2 that remain trapped until the candy reaches your mouth. There, the warm, damp conditions dissolve the sugar, and the gas escapes with a satisfying pop.
Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.