Chemical stability and colorant properties of betaxanthin pigments from Celosia argentea

The chemical stability and colorant properties of three betaxanthins recent ly identified from Celosia argentea varieties were evaluated. Lyophilized b etaxanthin powders from yellow inflorescences of Celosia exhibited bright y ellow color and high color purity with strong hygroscopicity. The aqueous s olutions containing these betaxanthins were bright yellow in the pH range 2 .2-7.0, and they were most stable at pH 5.5. The betaxanthins in a model sy stem (buffer) were susceptible to heat, and found to be as unstable as red betacyanins (betanin and amaranthine) at high temperatures (> 40 degreesC), but more stable at 40 degreesC with the exclusion of light and air. The th ree betaxanthins had slightly higher pigment retention than amaranthine/iso amaranthine in crude extracts at 22 degreesC, as verified by HPLC analysis. Lyophilized betaxanthins had much better storage stability (mean 95.0% pig ment retention) than corresponding aqueous solutions (14.8%) at 22 degreesC after 20 weeks. Refrigeration (4 degreesC) significantly increased pigment retention of aqueous betaxanthins to 75.5%.