Evaluation of Microencapsulated Turmeric Oleoresin for Pre-Extrusion Coloring Using Response Surface Methodology

Abstract

This work evaluates turmeric oleoresin (TO) vis‐à‐vis that microencapsulated in two wall materials, viz. gum arabic (TO‐GA) and n‐octenyl succinic anhydride (n‐OSA) starch (TO‐MS), as pre‐extrusion coloring of sorghum extrudate for maximum retention of color. The effect of the extrusion conditions on the retention of turmeric color during extrusion of sorghum flour – chosen as a model having parameters die temperature, screw speed and moisture content – was studied using response surface methodology. Experiments were carried out by extrusion of sorghum flour containing 1% oleoresin, and microencapsulated oleoresins using a single‐screw extruder at a constant feed rate of 55 g/min. At all conditions of extrusion, both the microencapsulated oleoresins gave a better retention of color than the free oleoresin. Experiments using the optimized levels of the parameters showed a good agreement between the experimental and the predicted values of color. PRACTICAL APPLICATIONS Natural colors are a diverse group of colorants with widely differing solubility and stability properties. As the majority of food and beverage products are water‐based, microencapsulation of colors is especially beneficial for pigments that are not soluble in water. Examples of these are various carotenoids such as β‐carotene, lutein, annatto and paprika, as well as turmeric, carmine and chlorophyll. Generally, coloring of the extruded products is done post‐extrusion. Hence, an attempt was made to evaluate microencapsulated turmeric oleoresin for pre‐extrusion coloring using response surface methodology.