French firm Fermentalg has been all over the planet in its search for useful microalgae.

"One of our lucky scientists got to go and climb the volcanoes in the Caribbean for example, and I have to restrain myself from collecting more every time I go home to New Zealand," says Hywel Griffiths, chief scientific officer at Fermentalg.

There are hundreds of thousands of species of microalgae - microscopic organisms, which mostly live in water. They are essential to the aquatic food chain and also produce half the oxygen we breathe.

Some are already used commercially, to make food, animal feed and fertiliser.

But for Fermantalg one particular type, Galdieria sulphuraria, has a very useful trait. It can be used to produce a pigment, suitable for use in food, called Galdieria blue.

"We grow the algae and make a lot of it under conditions which make a lot of this particular molecule - the blue," says Mr Griffiths.

The pigment can be used for any food and drinks and Mr Griffiths expects the first products using Galdieiria blue will be on shop shelves early next year.

Galdieria blue was approved by the US Food and Drug Administration (FDA) in May, along with Butterfly pea flower extract (also a blue colour) and calcium phosphate (white).

The FDA also approved Gardenia blue earlier this month.

New sources of colour for food are needed as artificial food dyes are on their way out.

In January,........

© BBC