Scientists have isolated a blue pigment from cultured soil bacteria that could offer a natural colouring with an excellent stability and toxicology profile for food.
The researchers, from the East China University of Science and Technology, report that the a blue pigment isolated from the Streptomyces coelicolor 100 strain taps into the trend for edible natural pigments.
Food makers have increasingly been looking for alternatives to artificial food colours such as Sunset Yellow, Tartrazine and Quinoline Yellow.
While the European colouring market faces an annual growth rate of just 1 per cent between 2001 and 2008, the colouring foodstuffs market is ripping ahead on growth of 10 per cent to 15 per cent.
"The good characteristics of the pigment give it potential for the food processing industry as an additive. It can be used to make some colourful beverages and cakes," wrote lead author Hechun Zhang in the journal Food Chemistry.
Zhang and colleagues obtained yields as high as three grams per litre after fermenting S. coelicolor 100 from soil, and, using high performance liquid chromatography (HPLC) found the blue pigment to be a mixture of ten compounds.
The solubility of the pigment was tested under acidic and alkaline conditions, and its stability was assessed on exposure to light and heat, and in the presence of oxidants and reducers at low pH (acidic) and to reducers at higher pH (alkaline).
The researchers state: "The pigment was stable to light and heat, and resistant to oxidants and reducers under acidic conditions and to reducers under alkaline conditions. [Moreover], no evident influences of food additives in common use, such as vitamin C and sodium benzoate, on pigment stability were observed."
An acute toxicity trial, carried out according to Evaluation Regulation of Food Safety in China (GB15193), confirmed that the pigment was non-toxic. The scientists evaluated the half-life lethal dose (LD50) using mice models and, during a 14-day trial with 70 mice receiving dose from zero to 15,000 mg/kg, no mice died.
"Thus, the pigment could be classified as a non-toxic substance according to the general toxicity standard," wrote Zhang.
None of the researchers were contactable prior to publication, and it is not known if an industrial partner is involved in further research and development of these pigments.
The study was supported by a grant from the Shanghai Key Discipline of Biochemical Engineering.
Source: Food Chemistry
Volume 95, Pages 186-192
"A kind of potential food additive produced by Streptomyces coelicolor: Characteristics of blue pigment and identification of a novel compound, ?-actinorhodin"
Authors: H. Zhang, J. Zhan, K. Su and Y. Zhang