Scientists have dug into a viral YouTube video from 2011 to solve the mystery of why grapes explode into fireballs when cooked together in a microwave oven.

The trio of researchers have published their work in the Proceedings of the National Academy of Sciences (PNAS).

They recreated viral videos which showed YouTubers cutting a grape in half, leaving only a sliver of skin connecting the two halves, and then microwaving the fruit.

Within seconds of being microwaves the two halves of a grape would suddenly explode into a fireball, despite not containing any obviously flammable material.

There were multiple hypotheses suggested at the time to explain the explosion, including that the grapes formed a kind of antenna directing microwaves across the skin bridge.

However, the real reason is even simpler.

As microwaves enter the grapes, hot spots form at the points where the fruit objects are closest to each other.

As the microwaves continue to heat the grapes, the hot spots get even hotter and the electrolytes surrounding them become supercharged, forming plasma – an ionised or electrically charged gas – which bursts in a fireball.

This method of producing plasma isn’t unique to grapes, and the researchers were able to replicate it in similar-sized fruit as well as water-filled balls.

They also found that a physical connection between the objects was unnecessary as the bond was driven by electric charge, they just needed to be close enough together.

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(c) Sky News 2019: Exploding grapes: Scientists figure out microwave mystery