3.5. Characterization of yellow Monascus pigments
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.