Optimization of pigment extraction from quinoa flour fermented by Monascus purpureus supplemented with sodium chloride

Monascus pigments as natural food dyes have been widely used in food industries around the world, and are known to provide antimutagenic properties, anticarcinogenic and antimicrobial activities and possible anti-obesity activities. Sodium chloride may contribute to the production of these beneficial secondary metabolites. The objectives of this study were: (1) To optimize the hydroethanol extraction of the pigments from quinoa flour fermented by M. purpureus; and (2) To establish a relationship to predict extract concentration (g/ml) by spectrophotometry of the hydroethanol extracts. The samples came from a solid-state fermentation of quinoa grains with M. purpureus supplemented with 0.5% sodium chloride (w/w) harvested on the eighth day. A Box-Behnken design (BBD) with a response surface model (RSM) were used to optimize the pigment extraction conditions of these flours. The extraction yield was 26.15±0.2607 under the optimized conditions (ethanol graduation of 50º, extraction temperature of 55ºC and ethanol: sample ratio of 40:1 (v/w). In addition, the best equation to predict extract concentration was linear and was attained by adding up absorbances measured at 400, 470 and 500 nm at a dilution of 1:6 (R²=0.958). This study demonstrated that the statistical design methodology was an efficient and feasible approach to determine the optimal conditions for the hydroethanol extraction of pigments from quinoa flour fermented by M. purpureus. Furthermore, a very useful equation for future predictions of extract concentrations was derived.