The advice is they should be eaten by a day or two after the "best-before" date, providing the eggs are cooked thoroughly until yolk and white are both solid, or if they are used in dishes where they will be fully cooked, such as a cake.

BBC: Should you smell food before throwing it away?

In early experiments, the researchers have used boiled eggs, with the Smart-Tool cutting through the egg white, but stopping when it reached the yolk.

BBC: Promise of touch technologies

Over time, the weaker yolk would devalue against the stronger white.

ECONOMIST: Why Europe��s leaders should think the unthinkable