The purified yellow Monascus pigments (44 mg/l in 70% ethanol aqueous solution) exhibited a visible spectrum with an apex at 395 nm, which was consistent with spectrum data in the literature [26]. One AU at 395 nm of yellow Monascus pigments corresponded to the concentration approximately 52 mg/l. The TLC analysis showed yellow Monascus pigments with Rf = 0.73, which was also consistent with the result of the literature [12] (Fig. 5A). It indicated that the yellow Monascus pigments were pure at least within visible spectrum. The results of Fig. 4 had already showed that the aminophilic reaction between yellow Monascus pigments and MSG did not occur or very slow comparison to that of orange
Monascus pigments and MSG. MSG (0.03 g) were added into an ethanol aqueous solution (70%, V/V, pH = 7; Yellow Monascus pigments with 0.685 AU at 395 nm; 24.6 ml), which was shaken at 30 C, 200 rpm and for 11 h. The visible spectrum of yellow Monascus pigments in the ethanol aqueous solution had nearly no change (Fig. 5B). This result further confirmed there was no aminophilic reaction between yellow Monascus pigments and MSG.