The humble spud could replace synthetic dyes and insect-based food colouring in the not too distant future. Until recently, extracting colorants from crops has posed a challenge to chemists. But now chemists from Texas A&M University have made a breakthrough that could see purple sweet potatoes as a source of pigments.
Purple sweet potatoes contain anthocyanins, the same chemical that clothes concord grapes in purple and gives raspberries a ruby hue. As a food colouring, anthocyanins could be used to create colours ranging from delicate pink to rose red to imperial purple. However, techniques for collecting the dyes from the plants tend to be expensive and inefficient compared to the production of other colorants.
"The natural colours industry for foods and beverages is gaining in value as the United States and international companies move towards sustainable and affordable crop alternatives to synthetic red colours and red colours derived from insects," says Stephen T Talcott of Texas A&M University.
"In addition to adding eye appeal to foods and beverages, natural colourings add natural plant-based antioxidant compounds that may have a beneficial effect on health." The left-overs from Talcott's process can be fed to livestock, used to produce biofuel or composted.
Currently, most red food colouring originates in a lab, while some comes from the cochineal insect. Approximately 2500 cochineal insects must be sacrificed to create one ounce of carmine, a red dye used in candy, yoghurt, ice cream and other foods.
