Study of saponification reaction in annatto pigments

This work aimed to evaluate the effect of different concentrations of KOH (1, 3 and 5%), time (1, 2, and 3 hours) and extraction temperature (30, 50 and 70 degrees C) on the saponification reaction of bixin. The reaction progress was monitored by High Performance Liquid Chromatography (HPLC) and by colorimetry, and the data were evaluated by regression analysis. Bixin and norbixin salt contents depended on NaOH concentration, while the extraction time did not present effect on the progress of saponification reaction. The best conversion of bixin to norbixin salt took place with the highest concentration of alkali,which was confirmed by colorimetric analysis. The increase of L-star, b(star), C-star, and H-star values were in agreement with the increase of norbixin salt content, whereas the reduction of a(star) was associated to the reduction of bixin content due to the conversion of bixin to norbixin salt. These results could contribute to modify the current production process of this pigment.