Einstein Science Reporting for Kids
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The color of cheese

This flower comes from the plant that produces bixin.
Click here for a high resolution photograph.

If milk is white, what makes cheddar cheese orange? The cheese coloring comes from a pigment called bixin. The Spanish name for bixin is annatto. Bixin comes from the bright red outer covering of the seeds of a tropical plant originally from South America. Today, this plant is grown around the world on farms. People harvest the seeds and use the red covering to make a pigment that adds color and texture to lots of foods and cosmetics.

Bixa seeds. The pigment used in foods and cosmetics comes from the bright red seed covers. Click here for a high resolution photograph.

Scientists in France and the Ivory Coast have now found a way to produce the pigment without growing the plant. Because the plant that produces bixin has no relatives that produce similar pigments, the scientists thought it would be useful to figure out another way to make bixin. They published their research in the 27 June 2003 issue of the journal Science. This discovery could increase the supply of bixin while reducing the need for harvesting the plants that produce it.

Bixa flower, fruits (A), seeds (B), wild E. coli (C) and the E.coli that can produce bixin (D). Click here for a high resolution photograph.

So how'd they do it? First, they figured out how the plant itself produces bixin. They found that bixin starts as a compound called lycopene (this is what makes tomatoes red). Then, the scientists saw that three plant genes are involved in turning lycopene into bixin. Bacteria called E. coli have already been engineered to produce lycopene. So the scientists took the three plant genes and put them into E. coli. Once the bacteria had the genes and the starting material, they started producing bixin. The bixin made by the bacteria is exactly the same as the bixin harvested from plants.

One day, with more research, scientists may be able to insert the three genes into a tomato and create "bixin factories" that can make more of the cheddar cheese coloring than the E. coli bacteria ever could.


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