What burnt actually means
Inside the pod is a coil — a wire wrapped in cotton. The cotton sits in the juice. When you pull, the coil heats the juice into vapour. Burnt happens when the cotton runs out of juice for a second; the wire heats dry cotton instead of liquid, and you taste scorched cotton. That's the only thing burnt is. Everything below is the same question: why wasn't the cotton wet when the coil fired?
