Abstract
Annatto dye is a natural organic dye belonging to carotenoids, whose main components are bixin and norbixin. Due to its low stability, it is convenient to protect the dye molecules with other materials. The use of clay minerals is an alternative, which are phyllosilicates with attractive physico-chemical properties, such as high specific surface area, cation exchange capacity, mechanical/chemical stability and non-toxicity. The main purpose of this work was to develop hybrid materials, using annatto dye and clay mineral modified with different inorganic cations, and then, to evaluate the stability of the new pigments. The process of preparing the modified clay minerals involved mixing a synthetic montmorillonite in solutions containing the precursor salts of the metal cations. Subsequently, the dye was dissolved in a solution containing water and alcohol, followed by filtration and mixed with the modified clay, giving rise to the hybrid pigments. Through the characterizations, it was noted that a variety of colors were obtained, and the sample containing aluminum was the one that most adsorbed the dye and showed a significant increase in stability at high temperatures. This hybrid material was better to dye than its pure form. Therefore, the bixin/montmorillonite pigments are promising for replacing artificial colors in practical applications such as in the cosmetics, food or pharmaceutical industries.
Highlights
Pigment is the term used to designate a solid, organic or inorganic particle, with specific colors or fluorescent, which is insoluble in the substrate in which it will be incorporated and does not promote any reaction with it [1,2].Annatto dye is a natural organic pigment belonging to carotenoids, being widely used as a food dye due to its low toxicity
The main purpose of this project was to develop hybrid materials, using annatto dye and clay modified with inorganic cations, aiming at the incorporation of bixin in the synthetic clay montmorillonite, and later to evaluate the stability of the new hybrid pigments
The amount of dye adsorbed and the nature of the metallic cations in the space between layers modified the structure of the pigments, influencing the difference, as to the color of the hybrids
Summary
Annatto dye is a natural organic pigment belonging to carotenoids, being widely used as a food dye due to its low toxicity This dye consists of two main components, which are bixin and norbixin [3]. It is less stable and discolored, so that light is the most destructive agent [4]. Basically composed of organic matter, magnesium and aluminum lamellar silicates, quartz, feldspars and metal oxides. They have clay minerals in their composition and among them, montmorillonite, which belongs to the smectite group, stands out
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