Oyster-friendly microalgae may colour food blue-green

Tag : green food
The compound called marennine, produced by the microalgae Haslea ostrearia, not only has potential to act as a pigment, but it also "exhibit[s] significantly higher antioxidative and free radicalscavenging activities than natural and synthetic antioxidantscommonly used in food," said a new study in the Journal of Agricultural and Food Chemistry .

The pigment shows excellent properties for use in foods, includinghigh water solubility, high resistance to heat and light, andstability at the pH range 6 to 8, according to researchers fromfive French universities and institutes.

"Of course, further metabolic and toxicological investigations areneeded to demonstrate that marennine could be used as a food gradesupplement, but no toxicity related to the pigment has ever beenreported during all the time marennine-greened oysters have beeneaten by humans," wrote lead author Jean-Bernard Pouvreau from the University ofNantes.

The market for natural colourings is growing, buoyed by consumers'concerns regarding artificial food colourings and flavourings.

The issue of artificial colourings came to a head with theFSA-funded study conducted at Southampton University and publishedin The Lancet last September. It concluded that cocktails of food colouringscommonly used in confectionery and beverages, and sodium benzoate,can aggravate hyperactivity in children.

For many consumers, particularly in Europe, blue colourings in foodare mostly associated with Nestle Rowntrees ' Smarties brand. The company stopped producing blue Smarties whenit promised to remove all artificial colourings from theconfectionery amid concerns that they are linked to hyperactivityand may pose other health risks.

The blue Smartie was replaced by a white one, while a suitablenatural alternative was found to the colouring Brilliant Blue (E133). After an extended period of development,the blue Smartie is now back thanks to Spirulina, which is producedfrom two species of cyanobacteria (blue-green lake algae).

New study

Pouvreau and co-workers evaluated marennine from Haslea ostrearia using two kind of antioxidant tests -antioxidant capacity assays, such as beta-carotene andthymidine protection assays, and iron reducing power assay, andassays scavenging DPPH, superoxide, and hydroxide free radicals.

The results showed that the pigment had a higher activity thatother natural and synthetic antioxidants commonly used in food,said the researchers. These included ascorbic acid, butylatedhydroxyanisole (BHA), and Trolox.

"The apparent antioxidant properties of marennine might bebeneficial to the antioxidant system of the human body and alsoraise the possibility of it being used as a protective agentagainst the oxidative damage of food products," wrote the researchers.

"Because of its blue-colouring property and water solubility, itcould also be used as a natural food-colouring additive," they added.

A rosy future for the blue-green pigment

The researchers noted that cultivation of the microalga would needto be optimised if marennine was to be produced industrially.Moreover, purification of the pigment would also need optimised.

Previous research by the same scientists, however, has alreadyproposed how this could be done. The technique " includes semipreparative technical procedures, like ultrafiltrationthrough membranes, which could easily be scaled up to a largerproduction system," they said.

Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, ASAP Article, doi:10.1021/jf073187n
"Antioxidant and Free Radical Scavenging Properties of Marennine, aBlue-Green Polyphenolic Pigment from the Diatom Haslea ostrearia(Gaillon/Bory) Simonsen Responsible for the Natural Greening ofCultured Oysters"
Authors : J.-B. Pouvreau, M. Morancais, F. Taran, P. Rosa, L.Dufosse, F. Guerard, S. Pin, J. Fleurence, P. Pondaven