The news will be welcomed by the European food industry, for which there has been high recent demand for natural colours to enable manufacturers to make all-natural claims for their products.
One of the recognised challenges surrounding natural colours is their lack of stability, creating problems when they are used in long shelf life products, such as ambient beverages.
Conventional ways of extracting anthocyanin from plant material are non-selective and yield pigment solutions with large amounts of byproducts, such as sugars, organic acids and proteins.
Some of these impurities may accelerate anthocyanin degradation, say the scientists, who are from the Department of Food Engineering, Central Food Technological Research Institute, Mysore, India.
The researchers tested several different extraction methods using different adsorbents. The best results were obtained using the Langmuir isotherm equation, especially at low temperature. The resulting anthocyanin solution after purification was free from sugars, which are the major cause for degradation of anthocyanin. In addition, no browning was observed and a 27% increase in colour was achieved.
A mixture of 50% ethanol and acidified water yielded the maximum degree of anthocyanin extraction, and non-ionic acrylic ester adsorbent Amberlite XAD-7HP showed the highest adsorption and elution, say the scientists.
Broad pH range
“Red cabbage is one of the sources of anthocyanins for colouration of food since its anthocyanins are unique, exhibiting colour over a very broad pH range. In contrast, anthocyanins from other sources such as grape skin, blackcurrant and elderberry, possess a reasonable degree of colour only at pH<4,” said the research team.
The colours yielded from anthocyanins derived from red cabbage range from red at high pH to blue and green at low pH.
“The evaluation of the final product with respect to total sugars, chroma [colour], browning and degradation index indicated an increase in the stability of anthocyanin after adsorption,” said the researchers.
Anthocyanins are also used in pharmaceutical products as powerful antioxidants with anti-inflammatory properties.
Source: Food and Bioproducts Processing
“Extraction of Anthocyanins From Red Cabbage and Purification Using Adsorption”; http://dx.doi.org/10.1016/j.fbp.2012.07.004
Authors: J Chandrasekhar; MC Madhusudhan; KSMS Raghavarao,