Extraction of dye sorghum biocolorant for the dyeing of wagashi, a West African soft cheese

We developed a sustainable method to extract the red biocolorant from dye sorghum leaf sheaths for dyeing <i>wagashi</i>, a West African soft cheese. The pigments were extracted using three different solvents: commercial ethanol (method A), <i>sodabi</i> (a local liquor distilled from palm wine; method B) and aqueous alkaline solvent (method C). In methods A and B, a pot still was used to distil and collect the solvent for reuse. The obtained extracts were used to dye <i>wagashi</i> at various concentrations. The yield and colour characteristics of the extracts were evaluated and the physicochemical characteristics of the dyed <i>wagashi</i> were recorded and compared to commercial <i>wagashi</i> sold in the local market. The solvent recovery in methods A and B was 96 % and 47 %, respectively. Extraction of anthocyanin pigments was highest with method A, namely 21 mg mL^-1 for total phenolics against 13.4 and 1.64 mg mL^-1 for methods B and C, respectively. The colour parameters suggested a similar colour for all the extracts, but the redness index of the extract from method B was significantly higher than that of the other methods. <i>Wagashi</i> dyed with extracts from methods B and C had similar colour characteristics and were comparable to the best-coloured commercial <i>wagashi</i> from the Parakou market based on the chroma and the hue angle values of the chromaticity diagram. Despite the lower colouring power of extracts made by method B, we consider this method the best when taking into account the cost and availability of the solvent. In conclusion, the application of <i>sodabi</i> extract at a dose of 200 mL L^-1 is recommended to dye <i>wagashi</i>.