Mayonnaise malaise

Mayo, that thick, creamy sauce used on sandwiches and salads. That leads us to today's brain teaser: Does mayonnaise have to contain eggs?

That somewhat bizarre question is at the centre of a corporate spat that could end up in the courts.

A US firm called Hampton's Creek has brought out a product, 'Just Mayo', that doesn't have any eggs in at all.

The multinational firm Unilever, maker of rival Hellman's, says mayo must contain eggs. So it's suing.

We talk it through with Alex Mackay, a chef, cookery teacher and writer.