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Colloidal approach to prepare colour blends from colourants with different solubility profiles.

Food chemistry (2013-06-26)
A R Patel, P C M Heussen, E Dorst, J Hazekamp, K P Velikov
ABSTRACT

Food colouring plays a vital and a determining role in the processing and the manufacturing of food products because the appearance of products is critical for attracting consumers and influencing their food choices. However, factors such as legislative restrictions, limited number of approved colourants and the processing, formulation and stability issues of the natural colourants severely limits the application of food colouring in actual product formats. Hence, finding alternatives to the currently utilised formulation practises, represents an important area of research. Here, we report a simple colloidal approach to prepare colour blends by co-incorporating colourants with contrasting aqueous solubility profiles in composite colloidal particles. Curcumin and indigocarmine were selected as water insoluble and water soluble food-grade colourants respectively and incorporated in the colloidal particles prepared from food protein-zein. Composite particles obtained by loading of curcumin and indigocarmine (at different ratios) had mean particle size ranging from 76 to 300nm. The spherical shape of the colloidal particles was confirmed using transmission electron microscopy and the colloidal dispersions were further characterised using UV-Vis and fluorescence spectroscopy. The incorporation of colourants in colloidal particles led to the generation of different shade of colour in yellow-green-blue range. The encapsulation also led to the stabilization of individual pigments against photodegradation. Such composite colloidal particles could potentially serve as an approach for developing tuneable colouring system for food and nutraceutical applications.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Indigo carmine, certified by the Biological Stain Commission, Dye content 85 %
Sigma-Aldrich
Indigo carmine, for microscopy (Bact., Hist.), indicator (pH 11.5-14.0)
Supelco
Indigo carmine, analytical standard
Sigma-Aldrich
Indigo, synthetic, Dye content 95 %